OF 


N.QN  CIRCULATING 

CHECK  FOR  UNBOUND 
CIRCULATING  COPY 


UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN  No.  266 


FACTORS   INFLUENCING 
LODGING   IN   CORN 

IN  COOPERATION  WITH  OFFICE  OF  CEREAL  INVESTIGATIONS 
BUREAU  OF  PLANT  INDUSTRY,  U.  S.  DEPARTMENT  OF  AGRICULTURE 

BY  BENJAMIN  KOEHLER,  G.  H.  DUNCAN, 

AND   ].    R.    HOLBERT 


URBANA,  ILLINOIS,  MAY,  1925 


CONTENTS 

PAGE 

METHODS  OF  EXPERIMENTATION* 311 

LEANING  STALKS  IN  CORN  GROWN  FROM  INFECTED  SEED 314 

Seed  Naturally  Infected  with  Fusarium  Moniliforme 314 

Seed  Naturally  Infected  with  Diplodia  zeae 314 

Seed  Naturally  Infected  with  Cephalosporium   acremonium 322 

Seed  susceptible  to  Scutellum  Rot 322 

Seed  Inoculated  with  Gibberella  saubinetii 328 

BROKEN  STALKS  IN  CORN  GROWN  FROM  INFECTED  SEED 332 

NONPARASITIC  FACTORS  INFLUENCING  LODGING. 334 

1.  Differences  in  Commercial   Strains 334 

• 

2.  Time  of  Planting 335 

3.  Rate  of  Planting 338 

4.  Previous  Cropping 339 

5.  Soil  Treatments 344 

6.  Yield 351 

COMPARISONS  OF  LODGING  IN  SELF-FERTILIZED  STRAINS 354 

1.  Nature  and  Behavior  of  Strains  Used 354 

2.  Correlation  of  Leaning  and  Root  Anchorage 355 

3.  Leaning   and    Pulling   Resistance    as    Related    to    Extent    of    Root 

Systems 357 

COMPARISONS  OF  STALK  BREAKING  IN  SELF-FERTILIZED  LINES  AND 

FIRST-GENERATION  CROSSES 364 

SUMMARY 369 

LITERATURE  CITED..  ..371 


FACTORS   INFLUENCING   LODGING 

IN   CORN 

BY  BENJAMIN  KOEHLER,  GEORGE  H.  DUNCAN,  AND  JAMES  R.  HOLBERT* 

Corn  (Zea  mays  indentata),  like  other  cereal  crops,  is  subject  to 
lodging.  The  relative  amount  of  lodging  in  different  cornfields  some- 
times varies  considerably,  and  speculations  on  the  cause  of  these  differ- 
ences have  not  answered  the  question  satisfactorily. 

From  the  time  corn  root  rot  investigations  were  first  inaugurated  in 
1917  by  one  of  the  authors,  Mr.  Holbert,  data  on  lodging  were  recorded 
in  order  to  determine  whether  or  not  this  condition  was  augmented  by 
seed  infection  with  some  of  the  corn  rot  organisms.  Recently  many 
corn  growers  and  investigators  have  gained  the  conception  that  lodging 
in  corn  is  caused  principally  by  the  corn  root  rot  diseases.  The  data, 
however,  have  not  always  verified  this  belief.  This  has  led  to  a  larger 
study  of  the  problem,  including  a  study  of  some  cultural  and  other  non- 
parasitic  factors  involved  as  well  as  of  the  inheritance  of  tendencies 
toward  weak  roots. 

METHODS  OF  EXPERIMENTATION 

Most  of  the  experimental  plots  on  which  data  on  leaning  and 
broken  stalks  were  obtained  were  located  near  Bloomington,  McLean 
county,  Illinois,  and  Urbana,  Champaign  county,  Illinois.  Some  data 
also  were  obtained  in  Knox,  Macon,  Rock  Island,  DeKalb,  Lee,  and 
Clark  counties  in  Illinois.  All  the  corn  was  grown  on  Brown  Silt  Loam 
with  the  exception  of  that  in  Clark  county,  which  was  grown  on  Yellow 
Silt  Loam. 

The  data  were  obtained  from  hand-planted,  carefully  controlled 
experiments  conducted  on  uniform  soil.  Each  experiment  included  a 
considerable  number  of  individual  plots  planted  alternately  with  nearly 
disease-free  and  with  diseased  seed.  The  individual  plots  usually  were 
four  rows  wide  by  ten  hills  long,  but  in  some  cases  they  were  larger. 
The  total  plant  population  of  all  replications  within  each  experiment,  as 
well  as  the  percentage  of  a  perfect  stand,  is  given  in  each  table  in  this 
bulletin.  The  rate  of  planting  varied  with  the  soil  productivity;  three 
kernels  a  hill  was  the  usual  number,  but  some  were  planted  at  the  rate 
of  two  kernels  a  hill.  All  the  plants  in  each  plot  were  included  in  the 
data  on  leaning  and  broken  stalks. 


•BENJAMIN  KOEHLER,  Associate  in  Crop  Pathology,  Illinois  Agricultural  Experiment  Station, 
formerly  Assistant  Pathologist,  Office  of  Cereal  Investigations,  U.  S.  Department  of  Agriculture; 
GEORGE  H.  DUNCAN,  Associate  in  Crop  Production,  Illinois  Agricultural  Experiment  Station;  JAMES  R. 
HOLBERT,  Agronomist,  Office  of  Cereal  Investigations,  U.  S.  Department  of  Agriculture. 

311 


312 


BULLETIN  No.  266 


[May, 


The  entire  plant  population  within  each  experiment  was  used  in 
obtaining  yield  data  except  in  a  few  experiments  in  which  only  the 
central  two  rows  of  each  individual  plot  were  used.  Yield  data  are  in- 
cluded in  most  of  the  tables  to  show  the  significance  of  seed  infection  or 
seed  inoculation.  Total  yields,  including  marketable  and  unmarketable 

grades,  are  given.  If  only  marketable  corn 
were  being  considered,  the  difference  be- 
tween the  yields  in  each  comparison 
usually  would  be  somewhat  greater. 

Nearly  disease-free  seed  and  diseased 
seed  used  in  each  experiment  were 
selected  not  only  from  the  same  strain 
but  from  stalks  that  were  grown  from  the 
same  seed  lot  and  in  the  same  field  dur- 
ing the  previous  year.  Methods  used  in 
making  these  selections  in  the  field,  on  the 
curing  racks,  and  on  the  germinator  are 
given  in  detail  by  Holbert  et  al.4  Except 
when  specifically  stated  that  certain  dis- 
eased seed  composites  were  comparatively 
starchy,  the  comparisons  were  made  be- 
tween nearly  disease-free  and  diseased 
composites  that  were  similar  in  appear- 
ance in  respect  to  composition,  both  be- 
ing horny.  The  diseased  seed  was  not 
infected  very  severely.  Only  ears  that  were  practically  100  percent  in 
viability  on  the  germinator  were  used  for  seed.  As  a  result  the  per- 
centage of  infection  ranged  not  higher  than  40  to  70  percent.  If  ears 
with  a  higher  percentage  of  infection  had  been  selected,  it  would  have 
been  impossible  to  obtain  enough  seed  ears  that  were  practically  free 
from  dead  kernels. 

The  diseased  seed  used  in  these  experiments  is  very  similar  to  that 
which  is  used  on  the  farms  where  a  germination  test  has  been  made  to 
discard  the  dead  ears.  However,  in  the  latter  case  a  mixture  of  infection 
is  usually  present,  while  in  the  work  herein  presented,  corn  infected 
with  the  several  organisms  has  been  separated  in  order  to  study  the 
symptoms  individually.  Ears  with  mixed  infection  were  discarded. 

Two  conditions,  apparently  independent  of  each  other,  were 
recognized  in  lodged  corn.  The  stalks  either  were  broken,  the  base  in 
that  case  usually  being  erect,  or  the  entire  stalk  inclined  because  of 
weak  root  anchorage.  Occasionally  the  base  of  broken  stalks  also 
inclined.  Such  plants  were  recorded  as  both  leaning  and  broken. 

In  nearly  every  case,  the  data  on  leaning  and  broken  stalks  were 
obtained  during  the  month  of  September. 


FIG.  1. — PROTRACTOR  USED  IN 
MEASURING  THE  ANGLES  OF 
DEVIATION  OF  CORN  STALKS 


1925]  FACTORS  INFLUENCING  LODGING  IN  CORN  313 

The  inclination  of  the  stalk  as  used  in  these  data  indicates  its 
deviation  from  a  vertical  position.  Fig.  1  illustrates  the  type  of  pro- 
tractor used  in  measuring  the  angles.  It  is  composed  of  three  strips  of 
wood  arranged  to  form  a  right-angled  triangle.  The  strip  forming  the 
hypotenuse  carries  the  degree  marks,  and  a  spirit  level  is  attached  to 
the  bottom  piece.  The  two  legs  of  the  triangle  are  each  thirty  inches 
long,  but  the  upright  one  has  an  extension  for  a  handle. 

Plants  leaning  30  degrees  or  more  were  counted  as  leaning  plants 
(Fig.  2);  those  leaning  less  than  30  degrees  were  disregarded.  During 
the  first  several  years  of  these  investigations  the  actual  inclination  of 
each  plant  was  recorded.  In  this  way  the  average  inclination  of  the 
plants,  as  well  as  the  percentage  of  plants  leaning  beyond  any  certain 
angle,  could  be  calculated.  This  method  consumed  a  great  deal  of  time, 
both  in  recording  the  data  in  the  field  and  in  summarizing  them  after- 
ward. Analysis  of  the  data  (Table  1)  showed  that  when  comparing 
plant  populations  grown  from  nearly  disease-free  seed  with  those  grown 
from  moderately  diseased  seed,  the  ratio  (1  to  1.52)  in  average  inclina- 
tion per  plant  was  practically  the  same  as  the  ratio  (1  to  1.55)  in  per- 
centage of  plants  leaning  30  degrees  or  more.  By  recording  field  data 
according  to  the  latter  system  only,  approximately  four  times  as  large 
a  population  could  be  covered  in  the  time  it  would  have  taken  by  the 
first  method.  In  this  way  greater  accuracy  was  obtained  because  larger 
populations  could  be  worked. 

Average  differences  in  leaning  stalks  and  broken  stalks  have  been 
analyzed  by  Student's  method9  to  obtain  the  odds  of  probability.  Odds 
of  30  to  1  or  more  are  considered  significant. 

Note. — In   the   tables,    reference   is  made  by  symbols,  abbreviations,  and  numbers 
to  the  various  strains  of  corn  used.   The  following  key  explains  them: 
BW.  A  strain  of  Burr's  White. 
BB.  A  strain  of  Bloody  Butcher. 
F-90.  Funk  90-Day. 

HY.  A  high-yielding  strain  developed  from  Reid's  Yellow  Dent  by  the  Univer- 
sity of  Illinois. 
K.  Funk  176-A  developed  from  Reid's  Yellow  Dent. 

C.  Griffin's  selection  from  Reid's  Yellow  Dent. 
P.  Paris'  selection  from  Reid's  Yellow  Dent. 
G.  Gulick's  selection  from  Reid's  Yellow  Dent. 

M.  McKeighan's  selection  from  Reid's  Yellow  Dent. 

A.  Atwood  and  Hauser's  selection  from  Reid's  Yellow  Dent. 

B.  Reid's  Yellow  Dent  supplied  by  LaSalle  County  Farm  Bureau. 

D.  Fox's  selection  from  Reid's  Yellow  Dent. 

S.  Sommer's  selection  from  Reid's  Yellow  Dent. 
77.  A  low-yielding  strain  of  Reid's  Yellow  Dent  from  Woodford  County  Farm 

Bureau. 
120.  Another  low-yielding  strain  of  Reid's  Yellow  Dent  from  Woodford  County 

Farm  Bureau. 
62.  A  high-yielding  strain  of  Reid's  Yellow  Dent  from  Woodford  County  Farm 

Bureau. 

101.  Another  high-yielding  strain  of  Reid's  Yellow  Dent  from  Woodford  County 
Farm  Bureau. 


314 


BULLETIN  No.  266 


[May, 


TABLE  1. — RATIOS  OF  LEANING  STALKS  IN  STRAIN  K,  YELLOW  DENT  CORN,  GROWN  FROM 

NEARLY  DISEASE-FREE  SEED  AND  FROM  MODERATELY  DISEASED  SEED 
Determined  by  average  inclination  of  plants,  and  percentages  of  plants  leaning  20°, 
30°,  45°,  and  60°,  respectively 


Exp. 
No. 

Condition  of  seed 

Stand 

Average 
degrees 
leaning 
per  stalk 

Percentage 
of  stalks 
leaning 
20°  or  more 

Percentage 
of  stalks 
leaning 
30°  or  more 

Percentage 
of  stalks 
leaning 
45°  or  more 

Percentage 
of  stalks 
leaning 
60°  or  more 

30 

1  038 

3  06 

6  13 

3.87 

2.69 

1  85 

922 

6  00 

10.86 

7.50 

4.92 

3.51 

Ratio  

1:1.96 

1:1.77 

1:1.92 

1:1.83 

1:1.90 

34 

1  413 

6  30 

14  40 

8  50 

4  62 

2  60 

1  322 

7  33 

16.35 

9.80 

7.24 

3  80 

Ratio  

1:1.16 

1:1.14 

1:1.15 

1:1.57 

1:1.46 

38 

290 

12  20 

31  72 

18  60 

8  33 

2  04 

275 

17  59 

46  23 

29  51 

14  54 

7  60 

Ratio  

1:1.44 

1:1.46 

1:1.59 

1:1.75 

1:3.73 

Average  ratio  

1:1.52 

1:1.46 

1:1.55 

1:1.72 

1:2.36 

LEANING  STALKS  IN  CORN  GROWN  FROM 

INFECTED  SEED 
SEED  NATURALLY  INFECTED  WITH  Fusarium  moniliforme 

Internal  seed  infection  with  Fusarium  moniliforme  Sheldon  is  very 
common  thruout  the  corn  belt.  The  fungus  is  of  a  pale  salmon  color  and 
grows  rapidly.  It  can  easily  be  detected  when  corn  has  been  tested  for 
a  period  of  seven  to  eight  days  on  a  good  germinator4.  Infected  ears 
frequently  have  an  excellent  appearance  and  many  pass  as  good  seed 
ears  unless  a  careful  germination  test  is  made. 

When  corn  infected  with  this  organism  is  grown  under  field  condi- 
tions, a  slight  reduction  in  stand  (Table  2)  and  early  vigor3  can  be 
noted.  In  seventeen  experiments,  extending  over  three  years,  the  yield 
was  reduced  in  nearly  every  instance,  the  average  being  68.0  bushels  per 
acre  for  corn  grown  from  nearly  disease-free  seed,  and  63.8  bushels  for 
corn  grown  from  Fusarium-infected  seed.  This  was  a  difference  of  4.2 
bushels  with  odds  of  832  to  1,  or  a  reduction  of  6.2  percent. 

The  percentage  of  leaning  plants,  however,  was  not  materially 
increased  by  seed  infection  with  Fusarium  moniliforme.  In  the  plots 
planted  with  nearly  disease-free  seed,  23.4  percent  of  the  plants  leaned 
30  degrees  or  more,  while  in  the  plots  planted  with  Fusarium-infected 
seed  24.3  percent  of  the  plants  leaned  to  the  same  extent.  The  differ- 
ence of  0.9  with  odds  of  7  to  1  is  not  very  significant.  It  seems  evident 
that  this  fungus  is  not  operative  as  a  root  rot  organism  to  the  extent 
that  it  weakens  the  anchorage  of  the  plant  in  the  soil. 

SEED  NATURALLY  INFECTED  WITH  Diplodia  zeae 

Diplodia  zeae  (Schw.)  Lev.  causes  the  common  dry  rot  of  corn. 
Only  a  small  proportion  of  the  infected  ears,  however,  become  badly 


1925] 


FACTORS  INFLUENCING  LODGING  IN  CORN 


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BULLETIN  No.  266 


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rotted.  Very  often  infection  is  difficult  to  detect,  and  frequently  it  be- 
comes evident  only  in  the  germination  test.4  Infection  of  seed  corn 
with  this  organism  results  in  a  greater  reduction  in  yield  than  infection 
with  any  other  organisms  herein  reported. 


Leaning  Broken 

FIG.  2. — Two  PHASES  OF  LODGING:    A  LEANING  STALK  AND  A  BROKEN  STALK 

The  leaning  stalk,  shown  at  the  left,  was  inclining  exactly  30  degrees.  Stalks  leaning 
to  this  extent  and  more  were  counted  as  leaning,  while  those  not  leaning  to  this  extent 
were  not  counted  as  such.  The  broken  stalk  shown  here  illustrates  a  typical  condition. 
The  break  may  occur,  however,  anywhere  along  the  length  of  stalk.  When  only  the 
tassel  was  broken,  the  stalk  was  not  counted  as  broken. 

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the  plumule  was  only  an  inch  or  two  in  length.  Similarly,  after  plant- 
ing in  the  field  plots,  many  seedlings  died  before  or  soon  after  coming 
thru  the  ground.  This  caused  a  considerable  reduction  in  s*tand  in 
every  case,  as  shown  in  Table  3.  Plants  that  lived  thru  the  seedling 


1925] 


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318 


BULLETIN  No.  266 


[May, 


stage  usually  developed  to  maturity,  but  they  did  not  produce  a  high 
average  yield  per  plant  commensurate  with  their  increased  opportunity 
due  to  a  thin  stand.  In  twenty-one  experiments  extending  over  three 
years,  the  plots  grown  from  nearly  disease-free  seed  averaged  69.1  bush- 


FIG. 


— 1LFFECT   OF 


LODGING 


A — A  plot  of  corn  grown  from  Diplodia-infected  seed,  in  which  13.7 
percent  of  the  plants  were  leaning  30  degrees  or  more. 

B — A  plot  grown  from  nearly  disease-free  seed  of  the  same  strain 
and  adjacent  to  the  one  shown  in  A.  Only  1.1  percent  of  the  plants 
leaned  30  degrees  or  more. 

els  per  acre,  while  those  grown  from  Diplodia-infected  seed  averaged 
46.7  bushels  per  acre.  This  is  a  difference  of  22.4  bushels  with  odds 
greater  than  9999  to  1,  or  a  reduction  of  32.4  percent,  a  very  serious  loss. 
In  every  experiment  except  one  (Table  3)  an  increase  in  the  per- 
centage of  leaning  plants  in  the  corn  grown  from  Diplodia-infected  seed 


7925] 


FACTORS  INFLUENCING  LODGING  IN  CORN 


319 


as  compared  with  that  grown  from  disease-free  seed  was  found  (Fig. 
3).  In  the  latter,  21.1  percent  of  the  plants  leaned  30  degrees  or  more, 
while  in  the  populations  grown  from  Diplodia-infected  seed  31.2  percent 
leaned  to  the  same  extent,  an  average  difference  of  10.1  with  odds 


Percentage  Increase 
in  Broken  Stalks 


Percentage  Increase 
in  Leaning  Stalks 


-20    -10      0     10     20    30  40    50       -50     10    20     30    40    50    60    70    80    90 


1921 
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Cephalosporium 
acremonium 


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7 


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Rot  -  Starchy 


G/bberella 
saubrnetn 


^^H  Probable  significant  increase      Wa%a  Probable  insignificant  increase 
"•  Evaluated  according  to  number  of  experiments  conducted  each  year 

FIG.  4. — PERCENTAGE  INCREASE  IN  BROKEN  AND  LEANING  STALKS  IN  CORN  GROWN 

FROM   INFECTED   SEED  AS  COMPARED   WITH  CORN   GROWN 

FROM   NEARLY    DISEASE- FREE  SEED 

greater  than  9999  to  1,  or  an  increase  of  47.8  percent  (Fig.  4).  Diplodia- 
infected  seed  caused  a  considerable  reduction  in  stand,  but  as  shown 
later  in  this  paper,  a  reduction  in  stand  would  tend  to  decrease  the 
percentage  of  leaning  plants,  and  not  to  increase  it. 

Diplodia  zeae  readily  causes  root  rot  of  seedlings  in  the  field,  as  well 
as  on  the  germinator.  In  nearly  every  case  infection  also  occurs  along 
the  base  of  the  plumule  on  the  part  that  later  becomes  the  mesocotyl. 
Many  plants  die  at  this  stage.  Those  that  survive  long  enough  to  de- 
velop secondary  roots  at  the  first  node  are  quite  likely  to  live  thruout 
the  season.  In  most  cases,  however,  the  mesocotyl  becomes  completely 
rotted  during  the  young  plant  stage.  The  primary  roots  (those  emerg- 


320 


BULLETIN  No.  266 


[May, 


ing  directly  from  the  kernel)  then  are  no  longer  able  to  function  and 
often  they  too  have  rotted  by  that  time.  This  causes  a  pronounced 
stunting  of  the  infected  plants  early  in  their  development  and  such 


FIG.  5. — ROOT  INJURY  CAUSED  BY  SEED  INFECTION  WITH  Diplodia  %eae 

A — The  crowns  of  two  corn  plants  grown  from  Diplodia-infected  seed,  sixty  days 
after  planting.  The  mesocotyl,  as  well  as  the  primary  roots,  are  brown  and  shriveled. 
The  secondary  roots  are  spindly  and  comparatively  few  in  number.  Such  plants  would 
be  expected  to  blow  over  easily. 

B — The  crowns  of  two  corn  plants  grown  from  nearly  disease-free  seed  and  the  same 
age  as  shown  above.  The  mesocotyls  are  bright  and  functioning,  and  all  the  roots  are 
in  a  vigorous,  healthy  condition. 

plants  naturally  do  not  develop  as  many  or  as  strong  secondary  roots 
as  normal  plants.     Fig.  5  illustrates  the  reduction  in  size  and  number 


1925~\  FACTORS  INFLUENCING  LODGING  IN  CORN  321 

of  roots  that  ordinarily  occurs  when  Diplodia-infected  seed  is  used. 
The  rotting  and  shriveling  of  the  mesocotyl  and  primary  roots  shown 
in  this  photograph  are  very  characteristic. 

As  one  would  expect  from  the  foregoing,  corn  plants  grown  from 
Diplodia-infected  seed  are  more  easily  pulled  up  from  the  soil  than 


FIG.    6. — PULLING    MACHINE    USED    IN    DETERMINING    THE    RELATIVE    ROOT 

ANCHORAGE  OF  VARIOUS  KINDS  OF  CORN 

The  essential  feature  of  this  machine  is  a  cross  beam  with  three  axes 
which  divide  it  in  the  ratio  of  1  to  9.  The  distal  axis  on  the  long  arm  of 
the  beam  is  hung  to  a  spring  balance  scale,  the  stalk  is  fastened  to  the  sec- 
ond axis,  and  a  steady  pull  is  exerted  on  the  other  distal  axis.  The  scale 
readings  are  then  multiplied  by  10  to  obtain  the  actual  pulling  resistance 
of  the  roots. 

plants  grown  from  disease-free  seed.  A  machine  has  been  described 
by  Holbert  and  Koehler5  by  which  corn  plants  can  be  pulled  up  easily 
and  the  pulling  resistance  of  the  plants  measured  in  pounds  (Fig.  6.). 
In  an  experiment  of  twenty-six  plots,  half  the  plots  being  planted  with 
Diplodia-infected  seed  and  the  alternate  half  with  nearly  disease-free 
seed,  15  hills  of  two  plants  each  were  pulled  in  each  plot.  The  aver- 
age pulling  resistance  for  plants  grown  from  Diplodia-infected  seed  was 
313  pounds  and  for  plants  grown  from  nearly  disease-free  seed,  337 — 
a  difference  of  24  pounds  per  plant,  with  odds  of  100  to  1  in  favor  of 
the  latter. 

The  rotting  of  the  primary  roots  and  mesocotyl,  with  a  resulting 
under-development  of  the  secondary  root  system,  seems  to  be  the  ex- 
planation for  the  occurrence  of  increased  percentages  of  leaning  plants 
when  Diplodia-infected  seed  is  planted. 


322 


BULLETIN  No.  266 


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19251  FACTORS  INFLUENCING  LODGING  IN  CORN  323 

SEED  NATURALLY  INFECTED  WITH  Cephalosporium  acremonium 

A  recently  discovered  corn  disease  known  as  the  black-bundle 
disease  has  been  described  by  Reddy  and  Holbert.7  It  is  caused  by 
Cephalosporium  acremonium  Corda,  a  very  small,  delicate  fungus. 
The  organism  is  carried  over  from  year  to  year  in  the  vegetative  stage 
within  the  seed.  During  the  germination  process  the  fungus  fructifies 
on  the  surface  of  the  kernels  and  an  experienced  person  can  readily 
identify  infected  kernels  by  the  use  of  a  microscope.  The  symptoms  of 
diseased  plants  become  more  or  less  evident  after  the  ears  have  reached 
the  milk  stage.  The  most  constant  symptom  is  the  presence  within  the 
stalk  of  several  to  many  blackened  vascular  bundles.  Other  symptoms 
of  the  disease  are  purple  midribs  of  leaves,  purple  stalks,  barrenness, 
nubbin  ears,  and  multiple  or  prolific  attempts  at  ear  formations. 

Two  years'  data  on  the  relation  of  seed  infection  with  Cephalo- 
sporium acremonium  to  leaning  stalks  were  obtained.  In  the  ten  experi- 
ments (Table  4)  the  average  reduction  in  yield  was  2.7  bushels  with 
odds  of  868  to  1.  The  percentage  of  leaning  stalks,  however,  was 
not  uniformly  affected.  In  five  experiments  infected  seed  apparently 
caused  an  increase  in  the  percentage  of  leaning  stalks,  while  in  the 
other  five  the  plants  behaved  in  that  respect  very  much  like  those 
grown  from  nearly  disease-free  seed.  On  the  whole,  plant  populations 
from  nearly  disease-free  seed  averaged  16.2  percent  leaning  stalks,  while 
those  from  infected  seed  averaged  18.7  percent,  a  difference  of  2.5  with 
odds  of  14  to  1.  From  the  two  years'  data  obtained  it  does  not  seem 
likely  that  corn  grown  from  seed  infected  with  Cephalosporium  acre- 
monium is  very  apt  to  incline  to  a  greater  extent  than  corn  grown 
from  healthy  seed. 

SEED  SUSCEPTIBLE  TO  SCUTELLUM  ROT 

Most  seed  that  has  not  had  rigid  selection  for  resistance  to  scutel- 
lum  rot  is  susceptible  to  this  disease.  It  is  the  most  common  disease 
in  field  corn.  Scutellum  rot  is  not  caused  by  an  organism  within  the 
seed  as  in  the  three  previously  discussed  diseases.  The  organisms, 
Rhizopus  spp.  and  some  others,  adhere  to  the  exterior  of  the  kernels 
and  gain  entrance  during  the  germination  process.  They  are  facultative 
parasites  that  are  common  everywhere,  and  perhaps  no  seed  corn  is 
entirely  free  from  them.  During  the  process  of  germination,  corn  sus- 
ceptible to  invasion  by  these  organisms  becomes  discolored  and  rotted 
in  the  scutellar  region.  Susceptible  kernels  often  are  covered  by  a  mass 
of  Rhizopus  mycelium  when  the  germination  test  is  completed  and  can 
be  detected  on  sight.  Frequently,  however,  scutellum  rot  can  be  de- 
tected only  by  bisecting  the  kernels  after  germination  and  examining 
the  scutellum.4 


324 


BULLETIN  No.  266 


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1925]  FACTORS  INFLUENCING  LODGING  IN  CORN  325 

The  yields  of  plots  planted  with  seed  susceptible  to  scutellum  rot 
have  practically  always  been  considerably  less  than  the  yields  of  similar 
plots  planted  with  nearly  disease-free  seed.  A  summary  of  the  stand, 
acre  yield,  and  leaning  plants  in  experiments  conducted  with  strain  K 
(Funk's  176-A)  yellow  dent  seed  is  given  in  Table  5.  This  strain  is 
very  popular  in  the  central  portion  of  the  corn  belt;  it  is  the  same 
strain  that  was  used  in  the  experiments  reported  in  Tables  1,  2,  3,  and  4. 
The  acre  yield  was  reduced  from  67.9  bushels  in  plots  planted  with 
nearly  disease-free  seed  to  59.8  bushels  in  plots  planted  with  seed 
susceptible  to  scutellum  rot.  This  is  a  difference  of  8.1  bushels  with 
odds  greater  than  9999  to  1,  or  a  reduction  of  11.9  percent.  There 
seems  to  be  no  doubt  but  that  decided  reductions  in  yield  are  caused 
by  this  disease.  Nevertheless,  the  percentage  of  leaning  stalks  was  in- 
creased very  little,  if  any,  as  compared  with  the  nearly  disease-free 
checks.  In  twenty  experiments,  leaning  was  increased  thirteen  times 
and  decreased  seven  times.  The  average  difference  in  percentage  of 
leaning  stalks  was  only  -{-2.2  with  odds  of  17  to  1,  which  is  hardly  sig- 
nificant. 

Experiments  with  seed  susceptible  to  scutellum  rot  in  other  miscel- 
laneous strains  of  yellow  dent  corn  are  summarized  in  Table  6.  The 
key  to  these  strains  is  given  on  page  313  under  "Methods  of  Experimen- 
tation." On  the  average  they  have  behaved  exactly  like  strain  K  sum- 
marized in  Table  5.  The  average  acre  yield  was  reduced  from  69.5 
bushels  to  60.7  bushels,  a  difference  of  8.8  bushels  with  odds  greater 
than  9999  to  1,  or  a  reduction  of  12.7  percent.  The  average  percentage 
of  leaning  stalks  was  increased  from  22.9  to  24.9,  a  difference  of  2.0 
with  odds  of  16  to  1.  Here  again  the  difference  in  percentage  of  lean- 
ing stalks  is  hardly  significant. 

In  all  the  experiments  reported  above,  the  diseased  and  nearly 
disease-free  seed  had  very  nearly  the  same  appearance  in  respect  to 
horniness.  None  of  it  could  be  classed  as  starchy.4-10  In  these  investi- 
gations starchy  seed  has  practically  always  proved  to  be  susceptible  to 
scutellum  rot.  Occasionally  a  starchy  ear  will  appear  to  be  disease- 
free  after  a  germination  test,  but  when  the  kernels  of  such  an  ear  are 
sprayed  with  a  spore  suspension  of  Rhizopus  spp.  before  the  test  is 
made,  scutellum  rot  develops  in  abundance.  When  disease-resistant 
horny  seed  is  sprayed  and  germinated  in  the  same  way,  scutellum  rot 
usually  does  not  develop. 

Table  7  gives  a  summary  of  twenty  experiments  over  a  period  of 
seven  years  on  the  comparative  field  performance  of  nearly  disease- 
free  horny  seed,  and  starchy  seed  susceptible  to  scutellum  rot.  The  av- 
erage acre  yield  was  reduced  from  71.1  bushels  to  59.6  bushels,  a  dif- 
ference of  11.5  bushels  with  odds  greater  than  9999  to  1,  or  a  re- 
duction of  16.2  percent.  It  should  be  noted  that  the  decrease  in  yield 
was  not  much  greater  than  it  was  when  horny  seed  susceptible  to  scutel- 


326 


BULLETIN  No.  266 


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328  BULLETIN  No.  266  {.May, 

lum  rot  was  compared  with  nearly  disease-free  horny  seed  (Tables  5 
and  6).  But  unlike  the  results  obtained  with  horny  seed  susceptible  to 
scutellum  rot,  the  plants  grown  from  starchy  seed  susceptible  to  scutel- 
lum  rot  leaned  considerably  more  than  those  from  nearly  disease-free 
horny  seed  (Table  7,  Fig.  4).  The  difference  in  percentage  of  leaning 
stalks  was  12.6  with  odds  greater  than  9999  to  1.  Trost10  has  pub- 
lished data  showing  an  increase  of  3.14  percent  leaning  stalks  and  53.0 
percent  down  stalks  when  corn  grown  from  disease-susceptible  starchy 
seed  was  compared  with  that  grown  from  disease-free  horny  seed. 

As  starchy  seed  susceptible  to  scutellum  rot  could  not  be  compared 
with  starchy  seed  resistant  to  this  disease,  it  could  not  be  determined 
whether  the  disease  was  the  principal  factor  in  producing  the  increase 
in  percentage  of  leaning  plants.  But  when  comparisons  were  made 
between  resistant  and  susceptible  seed  that  was  horny  in  composition, 
all  other  factors  being  as  comparable  as  could  be  obtained,  this  wide- 
spread disease,  even  tho  highly  detrimental  to  yield,  was  not  mani- 
fested to  any  appreciable  extent  in  the  form  of  leaning  stalks. 

SEED  INOCULATED  WITH  Gibber ella  saubinetii 

Gibberella  saubinetii  (Mont.)  Sacc.  is  the  principal  organism  caus- 
ing wheat  scab.  It  also  is  a  very  important  corn  root  parasite.* 

In  Illinois  the  organism  is  not  usually  seed-borne  on  corn  to  an 
important  extent.  Instead,  infection  occurs  principally  from  the  fungus 
overwintering  on  crop  refuse  on  and  in  the  soil.  For  that  reason,  up 
to  the  season  of  1924,  infected  seed  was  not  used  in  these  studies,  but 
experiments  were  conducted  by  inoculating  the  seed  with  a  pure  cul- 
ture of  the  organism  and  planting  on  virgin  soil.  At  planting  time  the 
seed  to  be  inoculated  was  moistened  with  a  spore  suspension  of  the 
organism.  Different  strains  of  corn  exhibiting  various  conditions  of 
seed  infection  were  used. 

Leaning  data  were  obtained  on  nearly  all  of  the  inoculation  ex- 
periments and  these,  as  well  as  stand  and  yield  data,  are  summarized 
in  Table  8.  In  each  experiment  where  nearly  disease-free  seed  and 
diseased  seed  of  the  same  strain  were  planted  in  comparative  tests,  the 
diseased  seed  usually  was  affected  to  a  greater  extent  by  inoculation 
with  Gibberella  saubinetii  than  was  nearly  disease-free  seed.  This 
seems  to  indicate  that  seed  resistant  to  certain  other  common  diseases 
also  is  more  resistant  to  injury  by  Gibberella  saubinetii. 

The  grand  average  of  all  the  data  in  Table  8  shows  a  considerable 
reduction  in  stand  and  yield  on  the  inoculated  plots,  and  an  increase 
in  the  percentage  of  leaning  stalks.  The  stand  was  reduced  9.8  percent. 
This  reduction  in  stand  alone  probably  would  not  have  greatly  influ- 

*Corn  disease  experiments  with  this  organism  have  been  conducted  at  Bloomington, 
Illinois,  for  a  number  of  years  in  cooperation  with  Dr.  J.  G.  Dickson.  of  the  Office  of 
Cereal  Investigations.  General  results  have  been  published  by  Holbert,  Dickson,  and 
Biggar,"  Koehler,  Dickson,  and  Holbert,8  and  Holbert  et  al.3'  *• 


/925]  FACTORS  INFLUENCING  LODGING  IN  CORN  329 

enced  the  yield,  as  all  these  plots  were  planted  at  the  rate  of  three 
kernels  per  hill.  The  yield,  nevertheless,  was  reduced  10.8  bushels  with 
odds  of  9999  to  1  or  12.9  percent. 

The  percentage  of  leaning  stalks  was  increased  from  12.4  in  the 
control  plots  to  15.4  in  the  inoculated  plots,  a  difference  of  3.0  with  odds 
of  2000  to  1,  or  an  increase  of  24.2  percent.  In  the  foreground  of  Fig. 


FIG.    7. — SEED    INOCULATED    WITH    Gibber ella    saubinetii 

A  row  of  com  in  which  every  alternate  hill  was  heavily  inoculated 
at  planting  time  with  Gibberella  saubinetn.  When  the  corn  had 
reached  the  hard  dough  stage,  nearly  all  the  plants  grown  from  in- 
oculated seed  went  down  in  a  rain  storm  while  nearly  all  the  con- 
trol plants  remained  erect. 

7,  a  row  of  Funk's  90-Day  corn  is  illustrated.  At  planting  time  the 
kernels  in  every  alternate  hill  had  been  heavily  inoculated  with  Gib- 
berella saubinetn. .  With  very  few  exceptions,  the  plants  grown  from 
the  inoculated  kernels  leaned  considerably  while  the  controls  stood  erect. 

When  germination  studies  were  made  of  the  1923  corn  crop  at 
Bloomington,  an  unusual  amount  of  seed  infection  with  Gibberella  sau- 
binetii  was  noted.  A  considerable  number  of  ears  showing  a  high  per- 
centage of  infection  but  possessing  good  viability  was  selected.  A 
composite  was  made  of  this  seed  and  tests  were  made  in  comparison 
with  nearly  disease-free  checks. 

Altho  only  one  year's  results  have  been  obtained  with  this  type 
of  seed  infection,  the  experiments  were  conducted  in  three  widely  sep- 
arated counties  within  the  state  and  the  results  check  closely.  The 
data  are  given  in  Table  9.  In  each  case  the  stand  was  considerably 
reduced  by  seed  infection,  with  results  similar  to  those  when  seed  was 
naturally  infected  with  Diplodia  zeae  (Table  3).  Seed  infection  also 
caused  an  increase  in  the  percentage  of  leaning  stalks  in  every  instance, 
the  grand  average  being  raised  from  25.7  percent  in  the  nearly  disease- 


330 


BULLETIN  No.  266 


[May, 


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Affected  with  scutellum-rot, 
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332 


BULLETIN  No.  266 


[A/ay, 


free  checks  to  31.9  percent  in  the  corn  grown  from  Gibberella-infected 
seed,  a  difference  of  6.2  with  odds  of  77  to  1,  or  an  increase  of  24.1 
percent.  The  least  difference  in  percentage  of  leaning  stalks  occurred 
in  Experiment  No.  98  in  Rock  Island  county.  Here  the  stand  was  cut 
the  most  by  Gibberella  infection.1  Thinness  of  stand  has"  a  tendency 

TABLE  9. — FIELD  STANDS  AND  AVERAGE  PERCENTAGES  OF  LEANING  STALKS  IN  STRAIN  K, 
YELLOW  DENT  CORN,  GROWN"  FROM  NEARLY  DISEASE-FREE  SEED  AND  FROM 
SEED  INFECTED  WITH  Gibberella  saubinettii,  1924 


Exp. 

No. 

County  in 
which  located 
(Illinois) 

Total  field  stand  of  all 
replications 

Average  percentage  of 
stalks  leaning  30°  or 
more 

Difference 
in   percent- 
age of  lean- 
ing stalks 

Nearly  disease- 
free  seed 

Gibberella-infected 
seed 

Nearly  dis- 
ease-free 
seed 

Gibberella- 
infected 
seed 

94 
95 
96 
97 
98 
99 

No. 
2  028 
1  948 
1  826 
1  901 
1  424 
2  949 

perct. 
87.9 
84.5 
86.7 
90.3 
73.3 
81.9 

No. 
1  693 
1  664 
847 
922 
429 
1  806 

perct. 
73.5 
72.2 
40.2 
43.8 
33.1 
50.2 

perct. 
39.8 
33.5 
29.8 
33.2 
7.0 
11.1 

perct. 
41.1 
41.0 
43.1 
44.1 
7.2 
14.7 

perct. 
+1.3 
+  7.5 
+13.3 
-4-10.9 

-i-  0.2 

+  3.6 

McLean  

Rock  Island  

Grar 

d  average  

84.1 

52.2 

25.7 

31.9 

+  6.2 
Odds  =  77:l 

to  make  the  plants  stand  more  erect  and  thus  offset  the  leaning  tendency 
(Table  12).  If  the  stands  had  been  equal  in  all  the  experiments,  the 
differences  in  percentage  of  leaning  stalks  would  no  doubt  have  been 
still  larger. 

The  results  shown  here  indicate  clearly  that  corn  root  rot  caused 
by  Gibberella  saubinetii  produces  an  increase  in  the  percentage  of  lean- 
ing stalks.  It  does  not  matter  whether  the  organism  is  placed  in  con- 
tact with  the  surface  of  clean  seed  as  was  done  in  the  inoculation  ex- 
periments, the  effect  being  comparable  to  soil  infection,  or  whether  the 
organism  is  seed-borne  from  infection  that  occurred  while  the  ear 
was  on  the  mother  plant.  Dickson1  has  shown  that  when  corn  is  in- 
oculated at  planting  time  with  a  spore  suspension  of  Gibberella  saubi- 
netii, and  grown  in  virgin  soil,  considerable  root  rotting  may  take  place 
in  the  seedling  stage.  It  is  not  yet  known  whether  this  organism  con- 
tinues its  activity  as  a  root  rot  organism  thruout  the  season  or  whether 
its  work  is  confined  to  the  young  plants.  Root  lesions  on  older  plants 
usually  are  not  abundant  and  isolations  from  them  have  not  given 
conclusive  results.  It  is  probable  that  the  increase  in  leaning  stalks  is 
caused  primarily  by  a  deficiency  in  the  number  or  extent  of  the  roots, 
due  to  root  rot  in  the  seedling  stage. 

BROKEN  STALKS  IN  CORN  GROWN  FROM  INFECTED  SEED 

While  some  of  the  corn  diseases  caused  considerable  increases  in 
the  percentages  of  leaning  plants,  usually  no  corresponding  increase  in 
the  percentage  of  broken  stalks  was  found  (Table  10).  A  significant 


1925} 


FACTORS  INFLUENCING  LODGING  IN  CORN 


333 


increase  in  percentage  of  broken  stalks  occurred  in  only  two  cases, 
namely,  when  seed  was  infected  with  Cephalosporium  acremonium  and 
when  starchy  seed  was  susceptible  to  scutellum  rot  (Fig.  4).  No  sig- 
nificant increase  in  percentage  of  broken  stalks  resulted  from  the  use 
of  seed  infected  with  Fusarium  moniliforme  or  Diplodia  zeae,  horny 

TABLE   10. — EFFECT  OF   SEED   INFECTION  AND   SEED   INOCULATION   ON   PERCENTAGE   OF 
BROKEN  STALKS:    SUMMARY 


Same  plant 
populations 
as  in  Table 

No. 

Strain 

Condition  of  seed 

Broken 
stalks 

Difference 
in  percent- 
age of 
broken 
stalks 

Odds 
of 
probabil- 
ity 

2 

K 

Nearly  disease-free  

perct. 
3.9 

perct. 

2 
3 

K 
K 

Infected  with  Fusarium  moniliforme  
Nearly  disease-free  

3.8 
3.5 

-0.1 

1:1 

3 

K 

4  0 

+0  5 

20-1 

4 

K 

4  0 

4 

5 

K 
K 

Infected  with  Cephalosporium  acremonium  .  .  . 

4.6 

5  7 

+0.6 

34:1 

5 

K 

6  2 

+0  5 

5-1 

6 

6  5 

6 

Affected  with  scutellum-rot  

6  2 

-0  3 

2:1 

7 

3  7 

7 

Miscellaneous 

Scutellum-rotted,  starchy  

4  5 

+0.8 

32:1 

8 

Miscellaneous 

Control  

4  2 

8 

Miscellaneous 

Inoculated  with  Gibberella  saulinetii  

4.2 

0.0 

seed  susceptible  to  scutellum  rot,  or  seed  inoculated  with  Gibberella 
saubinetii. 

With  one  exception,  none  of  the  organisms  concerned  in  these  seed 
infections  has  been  found  to  invade  the  stalk  higher  than  the  first  node 
immediately  above  the  mesocotyl,  as  long  as  the  plant  is  green.  In- 
vasion at  the  nodes  may  be  caused  by  Fusarium  moniliforme,  Gib- 
berella saubinetii,  Diplodia  zeae,  and  other  organisms,  but  this  is  due 
to  secondary  infection  from  spores  that  are  washed  down  between  the 
stalk  and  leaf  sheath,  and  is  not  concerned  with  seed  infection.  No 
doubt  these  local  infections  are  responsible  for  a  considerable  amount 
of  broken  stalks,  but  no  specific  data  on  these  relationships  have  been 
obtained. 

The  black-bundle  disease  caused  by  Cephalosporium  acremonium 
is  systemic,  and  seed  infection  with  this  organism  was  found  to  in- 
crease the  percentage  of  broken  stalks.  From  infected  seed  this  organ- 
ism may  invade  the  vascular  bundles  thruout  the  whole  length  of  the 
stalk  during  the  active  growing  period.  Affected  vascular  strands  be- 
come disorganized.  One  would  expect  this  to  reduce  the  breaking 
strength  of  the  stalks.  Furthermore,  at  times  a  more  or  less  local  de- 
composition of  the  pith  may  occur,  caused  perhaps  by  secondary  or- 
ganisms. This  causes  a  very  pronounced  weakening  of  the  stalk. 


334  BULLETIN  No.  266  {May, 

The  cause  of  more  broken  stalks  in  corn  populations  grown  from 
starchy  seed  affected  with  scutellum  rot  than  in  corn  populations 
grown  from  nearly  disease-free,  horny  seed  has  not  been  fixed 
very  definitely.  It  is  known,  however,  that  such  corn  is  also  more 
susceptible  to  some  other  diseases,  including  smut.  A  smut  boil  on  a 
stalk  causes  a  local  weakening  at  which  point  it  is  apt  to  break.  The 
significance  of  the  data  on  the  increase  in  broken  stalks  may  also  be 
questioned,  as  in  twenty  experiments  over  a  period  of  seven  years  the 
odds  are  only  32  to  1. 

As  the  other  organisms  do  not  invade  the  stalk,  no  increase  in 
the  percentage  of  broken  stalks  would  be  expected  except,  perhaps, 
as  the  plants  are  affected  by  malnutrition.  Malnutrition,  however, 
seems  to  result  not  so  much  in  decreasing  the  size  or  strength  of  the 
mature  stalks  as  it  does  in  reducing  the  yield. 

Rosen8  described  a  bacterial  disease  that  attacks  the  stalks,  as 
well  as  the  roots,  and  causes  many  stalks  to  break  over.  However,  as 
yet  he  has  published  no  data  on  broken  stalks  obtained  from  inocula- 
tion studies  or  otherwise.  Apparently  this  disease  is  seldom  found  in 
central  Illinois,  and  the  writers  were  not  able  to  obtain  any  data  on 
what  its  effects  might  be. 

NONPARASITIC  FACTORS  INFLUENCING  LODGING 

Some  of  the  nonparasitic  factors  influencing  lodging  are  so  well 
recognized  that  no  data  need  be  presented  in  that  connection.  Among 
these  are  seasonal  and  climatic  variations.  No  direct  comparisons  can 
be  made  between  the  percentage  of  leaning  plants  in  one  year  with 
those  in  another  year,  nor  can  direct  comparisons  be  made  between 
plots  that  are  located  at  some  distance  from  each  other  in  the  same 
year.  For  that  reason  it  is  necessary  to  have  a  well-organized  system 
of  checks  within  each  experiment.  Differences  between  the  checks  and 
the  corn  that  is  being  tested  can  then  be  compared  with  differences  ob- 
tained in  other  years  or  in  different  locations  within  the  same  year. 

A  number  of  nonparasitic  factors  other  than  seasonal  and  cli- 
matic variations  which  are  not  so  well  recognized  by  the  average  corn 
grower  have  also  been  found  by  the  writers  to  have  a  profound  influence 
on  lodging.  A  discussion  and  some  data  on  these  factors  are  presented 
here. 

DIFFERENCES  IN  COMMERCIAL  STRAINS 

Various  strains  of  corn  within  the  yellow  dent  group  exhibit  marked 
differences  in  the  way  they  stand  up.  A  number  of  strains  have  been 
tested  in  carefully  controlled  experimental  plots.  Nearly  disease-free 
selections  and  also  diseased  selections  of  these  strains  were  used. 

In  Experiment  20  (Table  6)  two  strains,  G  and  P,  were  used.  Grown 
from  nearly  disease-free  seed,  G  leaned  44  percent  more  than  P;  from 
diseased  seed  G  leaned  69  percent  more  than  P.  The  same  strains 
were  also  used  in  Experiment  22  (Table  6),  located  in  another  county 


1925]  FACTORS  INFLUENCING  LODGING  IN  CORN  335 

and  about  fifty  miles  north  of  Experiment  20.  The  results  were  quite 
similar;  from  nearly  disease-free  seed,  G  leaned  60  percent  more,  and 
from  diseased  seed  G  leaned  176  percent  more  than  P. 

In  Experiment  49  (Table  6)  strains  A,  B,  and  C  were  used  in  a 
comparative  test.  Grown  from  nearly  disease-free  seed,  the  percent- 
ages of  leaning  plants  were  respectively:  26.1,  34.1,  and  13.1;  from 
diseased  seed  they  were  24.9,  34.4,  and  17.3.  Thus  strain  C  stood  the 
most  erect  and  strain  B  inclined  the  most.  The  same  strains  were  also 
used  in  Experiment  51  (Table  8).  The  plots  of  this  experiment  were 
near  those  of  Experiment  49  and  the  results  were  very  similar;  C  stood 
the  most  erect  and  B  leaned  the  most. 

The  data  on  rate  of  planting  in  Table  12  cover  seventeen  different 
commercial  strains  of  yellow  dent  corn.  When  these  are  compared  with 
each  other  it  is  seen  that  their  behavior,  in  respect  to  percentage  of 
broken  and  leaning  stalks,  varies  greatly. 

Fig.  8  illustrates  the  conditions  of  two  strains  of  corn  at  harvest 
time.  Both  are  well  known  strains  of  the  corn  belt  that  mature  in  about 
100  days.  Only  nearly  disease-free  seed  of  both  strains  had  been  se- 
lected, they  were  planted  at  the  same  time,  and  were  grown  adjacent 
to  each  other  on  the  same  kind  of  soil.  There  was  very  little  difference 
in  the  stand.  Climatic  conditions  had  been  very  conducive  to  lodging 
during  the  season  (1924),  but  many  strains,  such  as  the  one  shown  in 
Fig.  8A,  stood  up  well,  while  some  others,  such  as  that  shown  in  Fig.  8B, 
went  down  almost  flat  to  the  ground. 

It  is  evident  that  when  two  strains  of  corn  are  grown  in  the  same 
field,  decided  differences  in  the  percentage  of  leaning  plants  may  oc- 
cur, owing  to  the  nature  of  the  plants.  As  corn  is  an  open-fertilized 
plant,  it  is  easily  changed  by  selection;  in  fact,  every  corn  grower  who 
has  systematically  selected  his  own  seed  corn  over  a  period  of  years 
has  a  distinct  strain  of  his  own.  Frequently  such  strains  show  differ- 
ences in  respect  to  percentages  of  leaning  or  broken  stalks. 

Different  strains  may  differ  in  their  susceptibility  to  disease,  and 
this  alone  might  account  for  differences  in  lodging.  However,  differ- 
ences in  lodging  also  often  result  from  factors  within  the  strains  en- 
tirely independent  of  the  disease  factor.  This  is  clearly  shown  by  the 
data  in  Table  6  in  which  nearly  disease-free  selections  of  various  strains 
are  compared  with  each  other,  and  scutellum-rotted  selections  of  the 
same  strains  also  are  compared  with  each  other.  Further  on  in  this 
bulletin  some  of  these  genetical  differences  will  be  discussed. 

TIME  OF  PLANTING 

Different  dates  of  planting,  ranging  from  early  to  late,  may  have  a 
marked  influence  on  the  percentage  of  leaning  plants  (Table  11).  It 
is  well  known  that  late-planted  corn  usually  does  not  yield  so  well  as 
that  planted  at  an  intermediate  or  early  date.  This  decrease  is  not  at- 
tributed to  increased  susceptibility  to  disease  but  chiefly  to  seasonal 


336 


BULLETIN  No.  266 


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19251 


FACTORS  INFLUENCING  LODGING  IN  CORN 


337 


conditions,  such  as  a  shorter  maturing  period  and  insufficient  depth  of 
the  root  system  when  the  summer  drouths  occur.  Data  given  by  Dick- 
son1  and  Holbert  et  al*  show  that  root  rot  by  Gibberella  saubinetii  is 
most  severe  when  corn  is  planted  early.  The  scutellum-rot  disease  is 
severe  in  both  early  and  late  planted  corn. 


FIG.  8. — SOME  VARIETIES  OF  CORN  LODGE  MORE  THAN  OTHERS 

These  illustrations  (A  and  B)  show  two  varieties  of  corn  in  Novem- 
ber, 1924,  both  grown  from  nearly  disease-free  seed  which  was  planted 
on  the  same  day  and  on  the  same  kind  of  soil.  Both  varieties  are  of 
the  100-day  class,  and  are  used  extensively  within  the  corn  belt. 

It  is  quite  evident  that  the  great  increase  in  percentage  of  leaning 
plants  in  late  corn  as  compared  with  early  corn  in  1920,  1921,  and  1923 
(Table  11)  was  not  due  to  disease  but  to  other  factors.  In  1922,  this 
condition  was  reversed,  the  smallest  percentage  of  leaning  plants  oc- 
curring in  the  last  planting.  In  1920,  the  percentage  of  broken  stalks 


338 


BULLETIN  No.  266 


[May, 


increased  with  the  later  dates  of  planting,  but  this  condition  was  re- 
versed in  1921  and  1923.  Evidently  it  is  not  possible  to  predict  with 
any  certainty  whether  late-planted  corn  will  lodge  more  or  less  than 
early-planted  corn,  but  a  difference  may  be  expected.  Just  what  factors 
are  operative  in  producing  these  differences  is  not  definitely  known,  but 
no  doubt  the  stage  of  development  of  the  corn  when  heavy  rains  or 
drouths  occur  is  largely  responsible. 

Two  adjoining  fields  of  commercial  corn  are  seldom  planted  at 
the  same  time.  Often  a  ten-day  interval  may  elapse.  When  this  is 
the  case,  considerable  differences  in  the  percentages  of  leaning  plants 
may  result  even  tho  the  same  strain  of  seed  was  used  and  all  of  it  tested 
nearly  disease-free.  Too  often  in  trying  out  new  seed  a  farmer  does 
not  plant  it  at  the  same  time  as  the  corn  with  which  he  will  make  the 
comparison  and  later  draws  erroneous  conclusions  when  he  finds  that 
one  strain  stands  up  much  better  than  the  other. 

RATE  OF  PLANTING 

Many  people  have  observed  that  the  rate  of  planting  may  materi- 
ally influence  the  amount  of  lodging  in  small  grains;  the  more  seed 
used  to  the  acre,  the  more  lodging  is  likely  to  occur.  The  present  writ- 

TABLE  12. — PERCENTAGES  OF  BROKEN  AND  LEANING  STALKS  IN  MISCELLANEOUS  STRAINS 

OF  CORN,  EACH  HAVING  BEEN  PLANTED  AT  THE  RATE  OF  Two  AND  THREE 

KERNELS  PER  HILL  IN  PARALLEL  SERIES.    CAMBRIDGE,  1923 


Strain 

Field  stand 

Broken  stalks 

Difference 
in  percent- 

Stalks leaning 
30°  or  more 

Difference 
in  percent- 

No. 

age  of  bro- 

age of  lean- 

2 kernels  per  hill 

3  kernels  per  hill 

2  kernels 

3  kernels 

ken  stalks 

2  kernels 

3  kernels 

ing  stalks 

No. 

perct. 

No. 

perct. 

•perct. 

perct. 

perct. 

perct. 

perct. 

perct. 

1 

76 

95.0 

112 

93.3 

2.6 

6.2 

+3.6 

13.2 

17.0 

+3.8 

2. 

73 

91.2 

105 

87.5 

13.7 

12.4 

-1.3 

13.7 

14.3 

+0.6 

3. 

73 

91.2 

102 

85.1 

8.2 

13.7 

+5.5 

15.1 

24.5 

+9.4 

4 

77 

96.2 

114 

95.0 

14.3 

7.0 

-7.3 

18.2 

15.8 

-2.4 

5. 

74 

92.4 

104 

86.7 

10.8 

22.1 

+11.3 

2.7 

17.3 

+14.6 

6. 

52 

65.0 

92 

76.7 

19.2 

12.0 

-7.2 

10.8 

19.6 

+8.8 

7. 

75 

93.7 

105 

87.5 

5.3 

17.1 

+11.8 

8.0 

7.6 

-0.4 

8. 

79 

98.8 

115 

95.8 

6.3 

12.2 

+5.9 

7.6 

23.5 

+15.9 

9. 

78 

97.5 

108 

90.1 

16.7 

9.3 

-7.4 

12.8 

16.7 

+3.9 

10. 

77 

96.2 

114 

95.0 

7.8 

H.9 

+7.1 

2.7 

10.5 

+7.8 

11. 

78 

97.5 

112 

93.3 

5.1 

9.8 

+4.7 

14.1 

14.3 

+0.2 

12. 

78 

97.5 

113 

94.2 

9.0 

10.6 

+  1.6 

9.0 

17.7 

+8.7 

13. 

75 

93.7 

111 

92.5 

6.7 

9.0 

+2.3 

14.7 

44.1 

+29.4 

14. 

79 

98.8 

115 

95.8 

8.9 

11.3 

+2.4 

15.2 

20.9 

+5.7 

15. 

78 

97.5 

114 

95.0 

15.4 

17.6 

+2.2 

19.2 

27.2 

+8.0 

16. 

77 

96.2 

101 

84.2 

6.5 

6.9 

+0.4 

19.5 

32.7 

+13.2 

17. 

80 

100.0 

119 

99.2 

11.3 

3.4 

-7.9 

17.5 

29.4 

+11.9 

94.0 

91.0 

9.9 

11.5 

+1.6 

12.6 

20.8 

+8.2 

Odds  =5:1 

Odds  = 

4999:1 

ers  have  made  some  similar  observations  in  respect  to  corn,  from  an 
experiment  conducted  by  J.  W.  Whisenand,  farm  adviser,  and  certain 
other  members  of  the  Henry  County  Farm  Bureau  (Table  12).  Tests 
for  rate  of  planting  were  conducted  with  seventeen  miscellaneous 
strains.  The  corn  was  planted  at  the  rate  of  two  and  three  kernels  to  a 


19251  FACTORS  INFLUENCING  LODGING  IN  CORN  339 

hill,  in  alternate  groups  of  four  rows  each.  Records  were  taken  on  only 
the  two  central  rows  of  each  group.  Thus  each  hill  on  which  data  were 
secured  was  completely  surrounded  by  hills  planted  at  the  same  rate. 

The  difference  in  rate  of  planting  between  two  and  three  kernels 
to  a  hill  had  practically  no  effect  on  the  percentage  of  broken  stalks,  the 
odds  of  the  difference  being  only  5  to  1.  But  the  percentage  of  leaning 
stalks  was  considerably  influenced,  being  raised  from  12.6  percent  to 
20.8  percent,  a  difference  of  8.2  with  odds  of  4999  to  1. 

These  data  are  especially  significant  in  connection  with  data  on  in- 
creases in  percentages  of  leaning  stalks  due  to  diseased  conditions,  when 
certain  kinds  of  infected  seed  were  used.  These  diseases,  especially  the 
Diplodia  seedling  rot,  cause  a  reduction  in  stand.  The  reduction  in 
stand  alone  would  tend  to  reduce  the  percentage  of  leaning  plants.  So 
when,  instead  of  this  decrease,  a  decided  increase  in  percentage  of  lean- 
ing plants  is  found,  the  increase  is  of  even  greater  importance  than  the 
figures  would  seem  to  indicate. 

PREVIOUS  CROPPING 

The  nature  of  the  previous  cropping  may  have  a  profound  influ- 
ence on  the  way  the  corn  stands  up.  A  comparison  of  corn  plots  grown 
in  1921  on  virgin  blue-grass  sod  with  similar  plots  planted  at  the  same 
time  in  a  rotation  which  was  75  percent  corn  is  given  in  Table  13.  The 
latter  plots  had  received  an  application  of  bone  meal  and  the  yields  were 
nearly  equal  to  those  on  virgin  sod.  Not  much  difference  occurred  in 
the  percentage  of  broken  stalks,  but  the  percentage  of  leaning  plants 
was  much  higher  on  the  plots  on  old  soil.  The  fifteen  checks  averaged 
22.3  percent  leaning  plants  on  the  virgin  soil  plots  and  32.5  percent  on 
the  old  soil  plots.  This  is  a  difference  of  10.2  with  odds  of  327  to  1,  or 
an  increase  of  46  percent.  The  average  of  the  fourteen  alternate  mis- 
cellaneous strains  gives  nearly  the  same  result. 

Table  14  gives  a  comparison  of  two  series  of  plots  in  1920,  one  fol- 
lowing two  years  of  clover,  the  other  having  previously  been  cropped 
with  badly  scabbed  spring  wheat  in  1919  and  corn  in  1918.  Ten  seed 
composites  were  used  and,  with  only  one  exception,  each  produced  a 
smaller  average  percentage  of  leaning  plants  on  the  plots  following 
clover.  When  all  ten  strains  were  averaged  together  a  significant  dif- 
ference with  odds  of  150  to  1  was  found,  owing  to  differences  in  previ- 
ous cropping. 

At  Urbana,  nearly  disease-free  seed  and  seed  susceptible  to  scutel- 
lum-rot  were  planted  in  comparative  plots  in  two  rotation  systems  for 
three  years.  In  one  system  (North-Central)  the  rotation  is  corn,  corn, 
small  grains,  and  clover;  and  in  the  other  (South-Central)  it  is  corn, 
corn,  corn,  and  soybeans.  Data  on  the  leaning  proclivities  of  the 
former  are  given  in  Table  15  and  Fig.  9.  On  the  three-year  average, 
corn  after  clover  had  5.5  percent  leaning  plants,  while  second-year  corn 


340 


BULLETIN  No.  266 


[May, 


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FACTORS  INFLUENCING  LODGING  IN  CORN 


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342 


BULLETIN  No.  266 


[May, 


after  clover  had  11.6  percent,  a  difference  of  6.1  with  odds  of  160  to  1, 
or  an  increase  of  110  percent. 

Similar  data  on  the  plants  grown  in  the  corn-soybean  rotation  are 
given  in  Table  16  and  Fig.  10.    With  the  exception  of  the  second  series 

TABLE  14. — LEANING  CORN  PLANTS  GROWN  FROM  SEED  COMPOSITES  OF  YELLOW  DENT 

OBTAINED  FROM  VARIOUS  SOURCES  IN  ILLINOIS 

All  seed  planted  at  the  same  time  in  adjacent  duplicate  plots.    One  plot  was  on  land 

that  had  been  in  clover  during  the  two  previous  years,  the  other  on  land  that  had  been 

cropped  with  badly  scabbed  wheat  in  1919  and  corn  in  1918.   Bloomington,  1920 


Seed 

Field  stand 
where  the  previous  crops  were: 

Percentage  of  stalks  lean- 
ing 30°  or  more  where  the 
previous  crops  were: 

Difference  in 

composite 
No. 

Clover  1919 

Spring  wheat  1919 

Clover  1919 

Spring  wheat 
1919 

percentage  of 
leaning  stalks 

Clover  1918 

Corn  1918 

Clover  191  8 

Corn  1918 

No. 

perct. 

No. 

perct. 

perct. 

perct. 

1. 

902 

85.4 

951 

90.0 

17.1 

35.7 

+  18.6 

2. 

852 

80.7 

938 

88.8 

9.6 

29.1 

+19.5 

3. 

908 

86.1 

926 

87.7 

4.7 

11.2 

+6.5 

4. 

860 

81.5 

866 

82.0 

7.0 

15.1 

+8.1 

5. 

897 

85.0 

857 

81.1 

2.6 

7.0 

+4.4 

6. 

853 

80.8 

860 

81.5 

8.8 

10.5 

+1.7 

7. 

733 

69.5 

779 

73.7 

7.8 

8.3 

+0.5 

8. 

840 

79.6 

849 

80.4 

4.2 

3.8 

-0.4 

9. 

795 

75.3 

825 

78.1 

5.9 

10.4 

+4.5 

10. 

820 

77.7 

766 

72.5 

10.8 

15.4 

+4.6 

Average 

846 

80.1 

861 

81.6 

7.9 

14.7 

+6.8 

Odds  =  150:1 

in  1921,  the  data  are  very  consistent.  Corn  after  soybeans  stood  most 
erect,  second-year  corn  after  soybeans  had  a  higher  percentage  of  lean- 
ing plants,  and  third-year  corn  after  soybeans  had  a  much  higher  per- 


TABLE    15. — PERCENTAGES   OF   LEANING   PLANTS   IN   STRAIN   K,   YELLOW  DENT  CORN, 

WHEN  GROWN  THE  FIRST  YEAR  AFTER  CLOVER,  AND  THE  SECOND 

YEAR  AFTER  CLOVER:    SUMMARY  OF  THREE  YEARS'  DATA 

Rotation  of  clover,  corn,  corn,  and  spring  grains,  at  Urbana 


Year 

Condition  of  seed 

Percentage   of   stalks   leaning 
30°or  more 

Increase 
of  B  over  A 

Previous  crop 
was  clover 
(A) 

Second-year    corn 
after  clover 
(B) 

1920 

Nearlv  disease-free  

perct. 
3.7 
4.2 

4.2 
6.0 

perct. 
9.8 
10.6 

4.7 
6.6 

+6.1 
+6.4 

+0.5 
+0.6 

1921 

7.7 
8.5 

6.3 
7.6 

26.7 
18.8 

20.3 
22.5 

+19.0 
+  10.3 

+14.0 
+14.9 

Nearly  disease-free  

Affected  with  scutellum  rot  

1922 

5.7 
2.7 

4.3 
5.2 

9.0 
2.0 

7.4 
1.0 

+3.3 
-0.7 

+3.1 
-4.2 

Affected  with  scutellum  rot  

Nearly  disease-free  

Average 

5.5 

11.6 

+6.1 
Odds  =  160:1 

7925] 


FACTORS  INFLUENCING  LODGING  IN  CORN 


343 


centage  of  leaning  plants.  The  average  of  the  three  years'  data  is  9.5, 
15.6,  and  24.6  percent  leaning  plants,  respectively,  for  first-,  second-, 
and  third-year  corn  after  soybeans.  The  odds  of  the  differences  are 

Percentage  of  Leaning  Stalks 


Crown  from  nearly  disease- free  seed 
5      10      15     20    25     30 


Grown  from  scute  Hum-rotted 'seed 
S       IO     15     20      25    30 


FIG.  9. — PERCENTAGES  OF  LEANING  STALKS  WHEN  CORN  FOLLOWED  A  PRE- 
VIOUS CROP  OF  CORN 


large  enough  to  remove  any  doubt  as  to  whether  the  differences  may 
be  due  to  chance. 

The  percentages  of  broken  stalks  on  the  corn-soybean  rotation 
varied  only  slightly  in  reference  to  previous  cropping.  The  differences 
were  not  great  enough  in  any  case  to  mean  anything  in  terms  of  odds  of 
probability. 

Percentage  of  Leaning  Stalks 

Grown  from  nearly  disease -free  seed       Grown  from  scutellum-rotted  seed 
S       10       15      20      15     30     35     40  10      t5      20      25     30     35      40 


Third 

year 

corn 

after 

soybeans 


FIG.   10. — PERCENTAGE  OF  LEANING  STALKS  WHEN  CORN  FOLLOWED  SOY- 
BEANS, WHEN  CORN  FOLLOWED  A  PREVIOUS  CORN  CROP,  AND  WHEN  CORN 
FOLLOWED   Two    SUCCESSIVE   CORN   CROPS 


344 


BULLETIN  No.  266 


[May, 


Increases  in  leaning  plants  on  land  that  has  previously  been  cropped 
with  corn  or  scabby  wheat  may  be  due  in  part  to  root  rot  by  Gibberella 
saubinetii,  but  this  fact  hardly  gives  a  complete  explanation.  This  or- 

TABLE    16. — PERCENTAGES  OF   LEANING   PLANTS  OF   STRAIN   K,   YELLOW   DENT  CORN, 

WHEN   GROWN  THE  FIRST,   SECOND,  AND  THIRD  YEARS  AFTER  SOYBEANS: 

SUMMARY  OF  THREE  YEARS'  DATA 

Rotation  of  soybeans  and  three  years'  corn,  at  Urbana 


Year 

Condition  of  seed 

Percentage    of   stalks    leaning 
30°  or  more 

Increase 
of  B  over 
A 

Increase 
of  C  over 
A 

Previous 
crop  was 
soybeans 

(A) 

Second 
year  corn 
after 
soybeans 
(B) 

Third 

year  corn 
after 
soybeans 

(C) 

1920 

perct. 
4.4 
4.6 

3.9 

4.2 

perct. 
9.1 
8.2 

4.7 
5.2 

perct. 
15.9 
18.5 

16.1 
17.3 

perct. 
+4.7 
+3.6 

+0.8 
+  1.0 

perct. 
+  11.5 
+13.9 

+12.2 
+13.1 

1921 

9.5 
9.5 

35.5 
23.5 

17.6 
22.5 

22.0 
18.6 

35.3 
20.6 

16.5 
14.6 

+8.1 
+13.0 

-13.5 
-4.9 

+25.8 
+11.1 

-19.0 

-8.9 

Affected  with  scutellum  rot  

1922 

Nearly  disease-free  

3.7 
2.1 

8.9 
4.6 

21.7 
15.6 

26.0 
16.8 

40.6 
37.5 

35.7 
27.0 

+  18.0 
+13.5 

+17.1 
+  12.2 

+36.9 
+35.4 

+26.8 
+22.4 

Nearly  disease-free  

Average 

9.5 

15.6 

24.6 

+6.1 
Odds  = 
•10:1 

+15.1 
Odds  = 
207:1 

ganism  causes  wheat  scab  and  corn  root  rot.  Koehler,  Dickson  and 
Holbert6  have  shown  that  the  yield  of  disease-susceptible  corn  was 
greatly  reduced  when  this  corn  was  grown  after  scabbed  wheat.  Dis- 
ease-resistant corn  was  not  affected  in  the  same  way.  The  nature  of 
the  previous  cropping,  however,  affects  the  leaning  of  corn  grown  from 
nearly  disease-free  (disease-resistant)  seed  as  well  as  that  grown  from 
diseased  seed. 

The  disease-free  seed  corn  selections  used  in  these  experiments 
have  shown  considerable  disease  resistance  when  inoculated  with  pure 
cultures  of  Gibberella  saubinetii.  Nevertheless,  plants  grown  from  this 
seed  behaved  very  differently  in  respect  to  percentages  of  leaning  plants 
when  grown  in  different  crop  sequences.  For  that  reason  it  is  not  be- 
lieved that  the  disease  factor  is  the  only  one  operative  in  this  connection. 

SOIL  TREATMEJ^TS 

The  application  of  agricultural  limestone  to  the  soil  at  the  rate  of 
4  tons  or  more  per  acre  resulted  in  a  marked  decrease  in  the  percentage 
of  leaning  plants.  Unburnt,  finely  ground  limestone  was  applied  at  the 
rate  of  4  tons  per  acre  in  all  the  experiments  except  numbers  30  to  36 


7925]  FACTORS  INFLUENCING  LODGING  IN  CORN  345 

inclusive  (Table  17).  In  these  the  applications  were  made  at  the  rate 
of  2,  4,  8,  12,  and  16  tons  per  acre.  The  2-ton  application  did  not  pro- 
duce much  effect  and  the  data  from  that  plot  are  not  included  in  the 
summaries  given  in  Table  17.  The  applications  of  4,  8,  12,  and  16 
tons  per  acre  produced  similar  results  and  the  data  from  these  ex- 
periments were  averaged  together. 

In  Champaign  county  the  experiments  were  conducted  on  long 
established  lime  plots  of  the  Experiment  Station.  Experiment  47  in 
McLean  county  was  conducted  on  plots  that  had  been  established  the 
previous  year.  All  the  others  are  first-year  results,  the  lime  having 
been  applied  in  the  spring  previous  to  planting  the  corn. 

A  summary  of  the  effect  of  lime  on  the  stand,  yield,  broken  stalks, 
and  leaning  plants  of  corn  grown  from  nearly  disease-free  and  from 
diseased  seed  is  given  in  Table  17.  The  stand  was  not  affected  to  any 
appreciable  extent,  nor  was  the  yield  increased  to  a  marked  extent  by 
lime.  In  Experiment  20,  conducted  in  Macon  county  in  1920,  there 
was  a  decided  increase  in  yield  due  to  lime.  Unfortunately,  the  soil 
plots  in  that  experiment  were  laid  out  with  only  one  no-treatment 
check  plot  and  hence  there  may  be  some  question  in  regard  to  soil  uni- 
formity. Practically  all  the  other  experiments  were  laid  out  so  that  a 
number  of  lime  plots  and  no-treatment  plots  were  alternated. 

On  the  whole,  yields  from  nearly  disease-free  seed  were  but  slightly 
affected  by  lime.  The  average  increase  in  yield  from  nearly  disease- 
free  seed  was  only  3.1  bushels  per  acre  with  odds  of  11  to  1,  which 
is  hardly  significant.  Yields  from  diseased  seed  were  increased  3.6 
bushels  per  acre  with  odds  of  127  to  1.  This  is  a  small  but  numerically 
significant  increase. 

The  percentage  of  broken  stalks  was  not  influenced  by  the  appli- 
cation of  lime. 

The  striking  effect  of  lime  was  the  decrease  in  percentage  of  lean- 
ing stalks.  In  practically  every  experiment  the  plants  stood  more  erect 
on  the  lime  plots.  In  the  grand  average  of  all  experiments  the  percent- 
age of  leaning  stalks  from  nearly  disease-free  seed  was  16.8  on  the  no- 
treatment  plots  and  12.6  on  the  limed  plots,  a  difference  of  4.2  with 
odds  of  876  to  1,  or  a  reduction  of  25  percent  (Fig.  11).  When  dis- 
eased seed  was  used  the  percentage  of  leaning  plants  was  reduced  even 
more,  the  difference  in  percentage  of  leaning  plants  being  6.5  with  odds 
of  9999  to  1,  or  a  decrease  of  29.8  percent  (Fig.  12). 

Data  on  leaning  and  broken  stalks  also  have  been  obtained  on  soil 
plots  treated  with  rock  phosphate,  acid  phosphate,  bone  meal  (Fig.  13) 
sodium  nitrate,  and  potassium  sulfate,  but  no  consistent  differences 
in  percentage  of  leaning  plants  or  broken  stalks  were  found.  Under 
certain  conditions  rock  phosphate  evidently  was  an  important  factor 
in  reducing  the  percentage  of  leaning  plants,  but  under  other  condi- 
tions no  such  effect  was  observed.  On  the  other  hand,  the  data  from 


346 


BULLETIN  No.  266 


[May, 


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348 


BULLETIN  No.  266 


[May, 


FIG.  11. — EFFECT  OF  LIMESTONE  ON  CORN  GROWN  FROM  NEARLY  DISEASE-FREE  SEED 
A — One  of  the  series  of  plots  of  yellow  dent  corn  grown  from  nearly  disease-free 

seed,  on  Brown  Silt  Loam  in  Knox  county.   The  soil  tested  slightly  acid.    In  this  series 

5.7  percent  of  the  plants  leaned  30  degrees. 

B — -One  of  the  series  of  plots  of  the  same  kind  of  corn  grown  alternately  with  those 

described  above,  but  on  soil  which  had  received  an  application  of  crushed  limestone  at 

the  rate  of  4  tons  per  acre.    In  these  plots  only  2.9  percent  of  the  plants  leaned  30 

degrees  or  more. 


7925] 


FACTORS  INFLUENCING  LODGING  IN  CORN 


349 


FIG.  12. — EFFECT  OF  LIMESTONE  ON  CORN  GROWN  FROM  STARCHY  SEED 
SUSCEPTIBLE  TO  SCUTELLUM  ROT 

A — A  plot  of  yellow  dent  corn  grown  from  starchy  seed  susceptible  to  scutellum 
rot,  on  Brown  Silt  Loam  in  McLean  county.  This  soil  gave  no  acid  reaction.  Plants 
from  this  type  of  seed  are  likely  to  lodge;  in  this  plot  18.2  percent  of  the  plants  leaned 
30  degrees  or  more. 

B — A  plot  of  yellow  dent  corn  of  the  same  strain  and  character  as  that  above  and 
grown  adjacent  to  the  same,  but  the  soil  had  received  8  tons  of  crushed  limestone  per 
acre.  In  this  plot  6.3  percent  of  the  plants  leaned  30  degrees  or  more. 


350 


BULLETIN  No.  266 


[May, 


FIG.  13. — EFFECT  OF  BONE  MEAL  ON  CORN  GROWN  FROM  SEED 
SUSCEPTIBLE  TO  SCUTELLUM  ROT 

A — One  of  a  series  of  plots  of  yellow  dent  corn  grown  from  seed  susceptible  to 
scutellum  rot  that  was  comparatively  horny  in  composition.  The  soil  was  a  Brown  Silt 
Loam  that  tested  slightly  acid.  On  these  plots  28.7  percent  of  the  plants  leaned  30 
degrees  or  more. 

B — One  of  a  series  of  plots  of  the  same  kind  of  corn  grown  alternately  with  those 
described  above,  but  on  soil  which  had  received  an  application  of  steamed  bone  meal  at 
the  rate  of  350  pounds  per  acre.  In  these  plots  only  12.9  percent  of  the  plants  leaned 
30  degrees  or  more. 


1925} 


FACTORS  INFLUENCING  LODGING  IN  CORN 


351 


lime  applications  were  quite  consistent  for  all  conditions  under  which 
these  investigations  were  conducted. 

It  is  evident  from  the  foregoing  that  the  presence  or  absence  of 
certain  soil  treatments  may  be  just  as  important  factors  in  causing 
variations  in  the  percentage  of  leaning  plants  as  any  of  the  corn  rot 
diseases.  It  is  not  known  why  lime  causes  a  more  erect  stand.  It 
apparently  does  not  control  corn  root  rot.  On  the  no-treatment  plots 
the  yields  from  nearly  disease-free  seed  averaged  70.8  bushels  while  the 
yields  from  diseased  seed  averaged  59.7  bushels,  a  reduction  of  11.1 
bushels.  On  the  limed  plots  the  yields  from  nearly  disease-free  seed 
averaged  73.9  bushels  while  the  yields  from  diseased  seed  averaged  63.3 
bushels,  a  reduction  of  10.6  bushels.  The  reductions  in  yield  from 
diseased  seed,  therefore,  were  practically  as  great  on  the  limed  plots, 
and  little  disease  control  by  lime  was  evident. 

YIELD 

On  first  thought  one  might  expect  barren  plants  to  stand  more 
erect  than  those  that  bear  heavy  ears.  Small  grains  lodge  to  a  much 
greater  extent  when  the  heads  are  heavy.  Similarly  the  limbs  of  fruit 
trees  bend  down  and  are  likely  to  break  when  heavily  loaded  with 
fruit.  This  analogy,  however,  usually  will  not  hold  for  corn.  In  a 
number  of  experiments  (Table  18)  the  plants  were  classified  according 
to  whether  they  bore  ears  or  nubbins  or  were  barren,  and  the  percentage 
of  leaning  plants  was  calculated  for  each  separately.  In  only  one  experi- 
ment out  of  five  did  the  barren  plants  stand  most  erect,  and  that  experi- 
ment embodied  the  smallest  populations  within  the  group.  When  the 

TABLE    18. — LEANING   CORNSTALKS   CLASSIFIED   ACCORDING   TO   WHETHER   THEY    BORE 

EARS  OR  NUBBINS  OR  WERE  BARREN 
Ears  =  6  ounces  or  over;  nubbins  =  less  than  6  ounces 


Year 

Experiment 
No. 

Variety 

Classification  of 
stalks  according 
to  yield 

Number 
of 
stalks 

Percentage  of 
stalks  leaning 
30°  or  more 

1917 

1 

Yellow  dent  .... 

Ear-bearing  

No. 
17  902 

perct. 
3.3 

1  185 

2.5 

2  213 

2.9 

1918 

5 

Bloody  Butcher. 

4  325 

3.2 

847 

4.6 

96 

14.6 

1918 

6  - 

Yellow  dent  

Ear-bearing  

11  766 
3  944 

15.2 

17.0 

471 

62.8 

1918 

7 

Yellow  dent  

Ear-bearing  
Nubbin-bearing  

2  025 
1  303 
510 

93 
6.4 
13.1 

1921 

58 

Yellow  dent  

Ear-bearing  
Nubbin-bearing  

800 
209 
86 

32.8 
33.2 
26.7 

12.8 

Average. 

12.7 

Barren.  .  . 

24.0 

352 


BULLETIN  No.  266 


[May, 


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FACTORS  INFLUENCING  LODGING  IN  CORN 


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354  BULLETIN  No.  266  [May, 

five  experiments  are  averaged,  the  results  are  as  follows:  ear  plants,  six 
ounces  or  over,  12.8  percent  leaning;  nubbin  plants,  less  than  six  ounces, 
12.7  percent  leaning;  and  barren  plants,  24.0  percent  leaning.  It  seems 
evident  that  in  these  corn  plots  conditions  usually  were  such  that  those 
factors  which  caused  barren  plants  also  caused  weak  root  anchorage. 

Variations  in  yield  seldom  are  correlated  with  similar  variations 
in  the  percentage  of  leaning  plants.  It  already  has  been  shown  that 
altho  all  the  previously  discussed  corn  diseases  cause  reductions  in  yield, 
not  all  of  these  diseases  cause  an  increase  in  the  percentage  of  leaning 
plants.  On  the  other  hand,  in  some  cases  the  yields  under  two  different 
conditions  may  be  the  same  while  the  difference  in  percentage  of  leaning 
plants  is  large.  In  1920  (Table  11)  early  and  late  corn  planted  with 
nearly  disease-free  seed  yielded  nearly  the  same,  but  the  latter  leaned 
much  more.  Table  13  gives  data  on  two  series  of  plots,  one  on  virgin 
soil,  the  other  on  a  rotation  which  was  75  percent  corn.  The  yield  on  the 
two  was  practically  the  same,  but  the  percentage  of  leaning  plants  on 
the  latter  was  much  higher. 

To  a  certain  extent,  those  conditions  that  produce  a  high  yield 
often  also  produce  a  high  percentage  of  erect  plants.  There  are,  how- 
ever, many  exceptions  to  this  statement,  and  on  the  whole,  differences 
in  percentage  of  leaning  plants  are  not  very  closely  associated  with 
differences  in  yield. 

COMPARISONS  OF  LODGING  IN  SELF-FERTILIZED  STRAINS 
NATURE  AND  BEHAVIOR  OF  STRAINS  USED 

This  discussion  will  be  confined  primarily  to  four  strains  which 
form  two  very  interesting  pairs  for  comparison.  Strains  A  and  B 
originated  from  two  selfed  plants  of  Reid's  Yellow  Dent  in  1917. 
Undesirable  progenies  were  dropped  each  year,  and  only  the  best 
appearing  plants  from  each  ear  were  selfed  for  further  propagation.  In 
1920,  no  successful  pollinations  avere  made  in  certain  of  the  good  lines 
and  so  the  ear  remnants  of  the  1920  planting  were  planted  again  in  the 
following  year.  This  is  indicated  as  R  in  the  pure-line  number. 

In  1923,  41  pure  lines  of  the  A  strain,  and  23  of  the  B  strain 
were  planted.  Data  on  these  and  their  ancestry  back  to  1919  are  given 
in  Table  19.  Many  more  pollinations  than  are  shown  in  the  table  were 
made  each  year,  but  only  such  ears  as  gave  good  germination  test  and 
superior  field  performance  were  continued  as  new  strains.  Summarized 
data  on  all  the  A  and  all  the  B  strains  are  presented  in  this  table.  Yield 
data  were  obtained  in  1919,  1920,  and  1923.  The  averages  of  the  two 
groups  are  very  similar  in  respect  to  yield.  Leaning  data  were  obtained 
each  year.  On  the  average,  the  B  group  leaned  much  more  than  the  A 
group.  Figs.  14  and  15  illustrate  the  appearance  of  the  plants  of  some 
of  these  strains  just  prior  to  harvest  time. 


1925} 


FACTORS  INFLUENCING  LODGING  IN  CORN 


355 


CORRELATION  OF  LEANING  AND  ROOT  ANCHORAGE 

Preliminary  data  on   the  correlation  of  leaning  plants  with  the 

pulling  resistance  of  the  roots  have  been  published  by  Holbert  and 

Koehler.5    In  1922  and  1923,  the  plants  of  a  number  of  the  A  and  B 

strains  were  pulled  to  determine  their  relative  root  anchorage.   All  the 


FIG.  14. — PURE-LINE  STRAINS  SHOW  STRIKING  CONTRAST  IN 

THEIR  ABILITY  TO  STAND  ERECT 

On  the  left,  a  row  of  the  weak-rooted  B  strain  inbred  for 
six  years.  On  the  right,  a  row  of  the  strong-rooted  A  strain 
inbred  for  the  same  length  of  time.  See  Tables  19,  20,  and  22. 

pulling  tests  within  each  year  were  made  under  uniform  conditions.  The 
hills  were  spaced  42  by  21  inches  apart  and  only  one  plant  was  grown 
to  a  hill.  The  averages  in  Table  19  show  that  the  A  strains  were  more 
firmly  rooted  than  the  B  strains,  the  resistance  being  227.4  pounds  in 
comparison  with  156  pounds  in  1922,  and  245.5  pounds  in  comparison 
with  206.2  pounds  in  1923. 

It  will  be  noted  that  pure-line  A-1-1-3-R-3  and  its  progeny  stand 
comparatively  erect  but  have  a  comparatively  low  pulling  resistance. 
This  probably  is  due  to  the  smaller  size  of  the  plants  of  this  strain; 
which  are  smaller  in  all  proportions  than  any  plants  of  the  B  strains 
or  of  pure-line  A-1-1-2-R-3.  Consequently,  they  are  well  anchored  in 


356 


BULLETIN  No.  266 


[May, 


comparison  with  their  size.  If  these  plants  did  not  have  a  diminutive 
habit  of  growth,  the  difference  in  pulling  resistance  between  the  A  and 
B  strains,  as  shown  above,  no  doubt  would  be  much  greater. 

All  the  B  strains  that  have  been  propagated  up  to   1923  are  of 
good  height  for  inbred  material,  and  comparisons  may  be  made  between 


FIG.  15. — STRONG  AND  WEAK  ROOT  ANCHORAGES  MAY  BE  INHERITED 
A  row  of  the  weak-rooted  inbred  B  strain  situated  between  two 
rows  of  the  strong-rooted  inbred  G  strain.  The  B  row  went  down  in 
a  rain  storm  toward  the  close  of  the  pollination  period.  Altho  the 
upper  half  of  the  stalks  had  gained  somewhat  of  an  upright  position 
when  this  photograph  was  taken,  the  basal  half  of  the  stalks  remained 
in  this  inclining  position  thruout  the  remainder  of  the  season.  The 
stalks  of  the  G  strain  in  these  rows  remained  erect  thruout  the  season. 

plants  of  the  different  pedigrees  in  regard  to  percentage  of  leaning 
stalks  and  pulling  resistance.  Considerable  variation  occurs  in  respect 
to  both  of  these  factors.  They  vary  inversely  to  each  other;  those  with 
the  highest  pulling  resistance  have  the  lowest  percentage  of  leaning 
plants.  Pulling  data  were  obtained  on  sixteen  strains.  The  average 
pulling  resistance  was  210.7  pounds.  If  the  strains  are  divided  into 
two  groups  of  the  eight  highest  and  eight  lowest,  the  average  pulling 
resistance  for  the  two  groups  will  be  281.5  and  140.0  pounds  respec- 
tively. Given  in  the  same  order,  the  average  percentage  of  leaning  plants 
for  each  of  the  two  groups  is  46.1  and  76.6  percent.  This  indicates  that 
the  two  factors  are  closely  correlated. 

In  the  A  strains,  pure-lines  A-1-1.-2-R-3  and  A-1-1-3-R-3  must  be 
compared  separately,  owing  to  their  different  habits  of  growth.   When 


1925]  FACTORS  INFLUENCING  LODGING  IN  CORN  357 

each  of  these  is  divided  into  groups  according  to  pulling  resistance,  it 
is  also  found  that  the  groups  with  the  highest  pulling  resistance  have  the 
lowest  percentage  of  leaning  plants. 

From  these  data  it  seems  that  a  strong  root  anchorage  is  the 
principal  factor  that  holds  the  stalks  in  an  upright  position.  It  has  often 
been  assumed  that  cornstalks  are  held  erect  primarily  by  the  propping 
function  of  brace  roots.  Well-developed  brace  roots  enter  the  soil 
several  feet  deep,  and  the  experience  of  the  writers  is  that  they  function 
much  more  as  anchorage  roots  than  they  do  as  brace  roots.  At  a  certain 
stage  of  development,  of  course,  the  brace  roots  have  barely  entered  the 
soil.  Most  lodging  of  corn  occurs  during  or  after  rains.  It  is  quite 
evident  that  the  bracing  function  of  short  brace  roots  is  practically  nil 
when  the  soil  is  soft.  That  is  why  the  percentage  of  inclining  plants 
correlates  very  closely  with  the  pulling  resistance. 

LEANING  AND  PULLING  RESISTANCE  AS  RELATED  TO  EXTENT  OF 
ROOT  SYSTEMS 

On  each  of  the  A  and  B  strains,  which  were  of  nearly  the  same 
size  above  ground  but  which  differed  greatly  in  regard  to  lodging  and 
pulling  resistance,  plants  were  selected  for  a  special  study  of  the  extent 
of  their  root  systems.  A  year  before  the  corn  was  planted,  two  parallel 
rows  of  sugar  barrels  were  placed  in  a  trench.  These  were  filled  with 
well-mixed,  screened  soil,  and  the  trench  was  filled  in  with  soil  around 
the  barrels  so  that  the  soil  surface  in  the  barrels  was  of  the  same  level 
as  that  of  the  surrounding  ground.  One  row  of  barrels  was  planted  with 
pure-line  A-l-l-R-3-2,  the  other  with  pure-line  B-1-1-1-R-8-2.  They 
were  planted  at  the  rate  of  two  kernels  to  a  barrel,  but  soon  after 
emergence  were  thinned  to  one  plant  to  a  barrel. 

When  the  plants  were  two  months  old,  the  soil  was  taken  away 
from  around  the  barrels  (Fig.  16),  the  hoops  were  cut,  and  the  staves 
removed.  The  soil  was  then  slowly  washed  away  from  the  roots  by  a 
stream  of  water  (Fig.  17).  Connections  were  made  with  a  drain  tile, 
so  that  the  water  drained  away  after  it  had  been  used.  Altho  the  plants 
were  barely  beginning  to  show  the  tassels  at  this  time,  a  number  of 
plants  of  the  B  strain  were  already  leaning  considerably  (Fig.  18). 

Data  on  the  results  of  this  experiment  are  given  in  Table  20.  As 
plants  1  and  2  had  suffered  some  damage  they  were  not  included  in  this 
table.  Data  on  the  remaining  eleven  plants  of  each  pure  line  are  sum- 
marized at  the  bottom  of  the  table.  It  will  be  seen  that  the  two  groups 
are  similar  in  height ,  the  A  strain  averaging  4.5  inches  taller.  There 
is  a  considerable  difference  between  the  two  groups  in  circumference 
of  stalks.  It  is  doubtful  whether  thickness  of  stalk  has  much  to  do  with 
extent  of  root  development.  An  HY  inbred  strain  has  an  unusually 
thick  stalk  but  is  very  weak-rooted,  whereas  a  tall,  slender-stalked  pure 
line  of  the  G  strain  is  strong-rooted. 


358 


BULLETIN  No.  266 


[May, 


The  great  difference  between  the  two  groups  that  accounts  for  the 
difference  in  lodging  and  pulling  resistance  is  in  the  number  and  extent 
of  the  roots.  This  is  shown  graphically  in  Fig.  19.  In  counting  the  roots, 
no  differentiation  was  made  between  brace  roots  and  non-brace  roots. 


FIG.  16. — PURE-LINE  CORN  STRAINS  GROWN  IN  BARRELS  So  THAT 
THE  ROOT  SYSTEM  COULD  BE  STUDIED  TO  BETTER  ADVANTAGE 
These  barrels  were  sunk  into  the  ground  and  filled  with  well- 
mixed,  screened  soil  a  year  before  the  corn  was  planted.  This  pho- 
tograph shows  the  soil  removed  from  around  the  barrels  prepara- 
tory to  opening  them  and  washing  the  soil  away  from  the  roots. 
Following  the  excavation  they  were  covered  with  wet  burlap  until 
they  were  opened.  The  row  of  barrels  marked  A  was  planted  with 
pure-line  A-1-1-2-R-3-2  and  the  row  marked  B  was  planted  with 
pure-line  B-1-1-1-R-8-2.  A  number  of  plants  in  the  latter  group 
had  been  leaning,  but  these  were  fastened  in  an  upright  position 
before  the  excavation  was  made. 

It  is  often  very  difficult  to  distinguish  between  the  two.  Many  roots  that 
have  their  origin  above  the  soil  level  penetrate  the  substratum  deeply 
and  apparently  have  the  same  function  as  those  that  have  their  origin 
lower  down.  Even  when  plants  of  the  same  pure  line  are  examined  it  is 
found  that  roots  from  similar  nodes  may  appear  above  ground  on  one 
plant  and  below  ground  on  another. 

Plants  of  the  A  strain  not  only  had  more  roots  but  they  branched 
much  more  and  the  branches  were  longer  (Fig.  20).  This  is  shown 
statistically  in  the  air-dry  weights  of  the  roots  (Table  20).  The  average 


1925}  FACTORS  INFLUENCING  LODGING  IN  CORN  359 

air-dry  weights  of  the  roots  of  the  B  strain  were  only  53.0  percent  as 
heavy  as  those  of  the  A  strain  (Fig.  19). 

Another  root  study   parallel  to  that  above  was  conducted  with 
strong-rooted  and  weak-rooted  progenies  of  the  G  strain.    These  were 


FIG.  17. — REMOVING  THE  SOIL  FROM  THE  ROOTS 
Each  barrel  was  first  removed  from  its  orig- 
inal position  until  it  had  a  clearance  of  about 
a  foot  all  around.  The  hoops  were  then  cut 
and  the  staves  removed.  The  stalk  was  tied 
in  an  upright  position.  Plenty  of  water  was 
applied,  but  with  little  force,  at  the  top  of  the 
soil  until  it  was  all  washed  away. 

planted  at  the  same  time  and  harvested  only  a  few  days  later  than 
those  of  the  A  and  B  strains  above.  In  this  case,  the  plants  of  the 
two  groups  averaged  very  closely  not  only  in  plant  height  but  also  in 
number  of  roots  (see  Table  21  and  Fig.  21);  but  the  roots  of  G-4-2-1 
were  profusely  branched  while  those  of  G-4-4-1  were  but  slightly 
branched.  This  caused  a  great  difference  in  dry  weight  of  the  roots, 
those  of  the  weak-rooted  strain  weighing  only  43.5  percent  as  much  as 
those  of  the  strong-rooted  strain  (Fig.  21). 

Further  data  on  the  field  performance  of  plants  of  the  strains  just 
discussed  is  given  in  Table  22.  It  shows  the  respective  pulling  resistance 
of  the  four  strains  as  measured  by  the  average  values  for  fifty  plants  in 


360 


BULLETIN  No.  266 


[May, 


FIG.   18. — BEHAVIOR  OF  STRONG-ROOTED  AND  WEAK-ROOTED 
SELF-FERTILIZED  STRAINS 

On  the  left,  plant  21  of  pure-line  A-1-1-2-R-3-2,  standing  erect. 
On  the  right,  plant  22  of  pure-line  B-1-1-1-R-8-2,  leaning  40  de- 
grees. Data  on  both  of  these  plants  are  given  in  Table  20.  Pho- 
tographed when  plants  were  61  days  old.  Fig.  20-A  shows  these 
same  plants  on  the  same  day  after  the  soil  had  been  removed 
from  the  roots. 


Average  plant  height 
abort  ground 

Average  circumference 
at  base  of  stalks 


Average  number  of 
roots  per  plant 

Average  air-dry  iveight 
of  aerial  parts 

Average  air-dry 
weight  of  roots 


FIG.   19. — CERTAIN  CHARACTERISTICS  OF  STRAIN   B-1-1-1-R-8-2   AS  COMPARED  ON  A 
PERCENTAGE   BASIS  WITH  STRAIN  A-1-1-2-R-3-2 

Strain  A-1-1-2-R-3-2  in  each  case  represents  100  percent.     From  data   shown  in 
Table  20. 


1925~\ 


FACTORS  INFLUENCING  LODGING  IN  CORN 


361 


FIG.    20. — ROOT    SYSTEMS    OF    STRONG-ROOTED    AND    WEAK-ROOTED    SELF-FER- 
TILIZED STRAINS 

A— On  the  left,  pure-line  A-1-1-2-R-3-2.  On  the  right,  pure-line  B-1-1-1-R-8-2, 
harvested  61  days  after  planting.  The  figures  on  the  margin  indicate  distance 
in  feet.  These  two  plants  are  shown  in  their  original  environment  in  Fig.  18. 
Altho  the  heights  of  the  aerial  parts  of  these  two  plants  were  practically  the 
same,  the  air-dry  weights  of  their  roots  were  130  and  44  grams,  respectively. 
The  latter  plant  leaned  about  40  degrees.  This  was  caused,  no  doubt,  by  in- 
sufficient root  anchorage.  The  difference  is  due  primarily  to  genetic  factors. 

B — Two  plants  of  the  same  age  and  same  pedigrees  as  shown  in  A.  One  of 
the  plants  had  been  blown  down  in  the  young-plant  stage,  owing  no  doubt  to  in- 
sufficient root  anchorage;  later  it  elbowed  back  into  a  vertical  position.  This 
condition  is  often  seen  in  ordinary  cornfields.  The  air-dry  weights  of  the  roots 
were  98  grams  for  the  straight  plant  and  54  grams  for  the  elbowed  plant. 


362 


BULLETIN  No.  266 


[May, 


TABLE  20. — MEASUREMENTS  AND  WEIGHTS  OF  STALKS  AND  NUMBER  AND  WEIGHTS  OF 

ROOTS  OF  Two  SELF-FERTILIZED  STRAINS  OF  CORN,  ONE  (A-1-1-2-R-3-2) 

HAVING  A  STRONG  TENDENCY  TO  STAND  ERECT  AND 

THE  OTHER  (B-1-1-1-R-8-2)   TO  LODGE 

Planted  May  22  and  harvested  July  19  to  23,  at  Bloomington,  1923 


Pure-line  No.  A-1-1-2-R-3-2 

Pure-line  No.  B-1-1-1-R-8-2 

Plant 
No. 

Height 
of 
plant 

Circum- 
ference 
of  stalk 

Number 
of 
roots 

Air-dry  weight 

Plant 
No. 

Height 
of 

plant 

Circum- 
ference 
of  stalk 

lumber 
of 
roots 

Air-dry  weight 

Aerial 
parts 

roots 

Aerial 
parts 

roots 

inches 

inches 

grams 

grams 

inches 

inches 

grams 

grams 

3 

45.5 

2.6 

33 

62 

40 

4 

39.8 

1.8 

28 

20 

19 

5 

49.0 

3.0 

48 

84 

47 

6 

39.5 

1.5 

14 

20 

9 

7 

59.  5 

3.5 

48 

120 

103 

8 

52.0 

2.0 

20 

42 

17 

9 

50.5 

3.4 

47 

102 

100 

10 

49.8 

2.3 

24 

52 

50 

11 

58.0 

3.0 

42 

98 

47 

12 

54.0 

2.0 

30 

60 

32 

13 

65.0 

3.8 

62 

105 

93 

14 

54.0 

2.8 

38 

56 

36 

15 

59.0 

3.3 

56 

82 

72 

16 

58.0 

2.9 

39 

82 

72 

17 

64.0 

3.5  . 

58 

92 

98 

18 

66.0 

1.8 

47 

110 

85 

19 

68.0 

3.5 

45 

88 

68 

20 

59.0 

2.8 

38 

86 

46 

21 

71.0 

4.0 

63 

130 

110 

22 

66.0 

2.9 

47 

115 

44 

23 

54.0 

3.0 

41 

88 

98 

24 

56.0 

2.6 

31 

62 

54 

Average 

58.5 

3.3 

49.4 

95.5 

79.6 

54.0 

2.3 

32.4 

64.1 

42.2 

each  group  in  1922,  the  pulling  resistance  of  an  extreme  representative 
of  each  strain  selected  for  propagation,  and  the  average  pulling  resist- 
ance of  the  respective  progenies  of  these  extreme  individuals.  It  will  be 
noted  from  the  table  that  each  of  these  four  parent  plants  differed 
markedly  from  the  average  value  of  the  population  from  which  it  was 
chosen. 

The  four  progenies  grown  in  1923  then  represent  the  offspring  of 
the  strongest  plant  in  each  of  the  two  strong  strains  and  of  the  weakest 
plant  in  each  of  the  weak  strains.  As  shown  in  Table  22,  by  the  average 
values  of  the  progenies,  the  strong-rooted  and  weak-rooted  strains 
differed  more  widely  in  their  average  pulling  resistance  than  did  the 
parental  population  of  fifty  plants,  but  they  did  not  differ  so  widely  as 

TABLE  21. — MEASUREMENTS  AND  WEIGHTS  OF  STALKS  AND  NUMBER  AND  WEIGHTS  OF 

ROOTS  OF  Two  SELF-FERTILIZED  STRAINS  OF  CORN,  ONE   (G-4-2-1)  COMING 

FROM  A  FIRMLY  ROOTED  PLANT  AND  THE  OTHER  (G-4-4-1) 

FROM  A  PLANT  EASILY  PULLED  UP 
Planted  May  22  and  harvested  July  21  to  25,  at  Bloomington,   1923 


Pure-line  No.  G-4-2-1 

Pure-line  No.  G-4-4-1 

Plant 
No. 

Height 
of 
plant 

Circum- 
ference 
of  stalk 

Number 
of 
roots 

Air-dry  weight 

Plant 
No. 

Height 
of 
plant 

Circum- 
ference 
of  stalk 

Number 
of 
roots 

Air-dry  weight 

Aerial 
parts 

roots 

Aerial 
parts 

roots 

inches 

inches 

grams 

grams 

inches 

inches 

grams 

grams 

1 

56 

2.8 

39 

108 

63 

2 

58 

1.9 

50 

42 

32 

•» 

66 

2.8 

57 

114 

122 

4 

66 

2.3 

44 

82 

64 

5 

60 

2.3 

35 

78 

44 

6 

58 

2.0 

34 

58 

42 

7 

60 

2.8 

38 

82 

44 

8 

62 

2.2 

37 

56 

26 

9 

67 

3.0 

52 

166 

152 

10 

68 

2.5 

57 

108 

56 

11 

73 

3.0 

48 

149 

115 

12 

67 

2.5 

47 

86 

32 

13 

70 

2.6 

44 

106 

98 

14 

70 

2.9 

52 

78 

66 

15 

72 

3.1 

59 

172 

127 

16 

66 

2.5 

49 

68 

54 

17 

63 

2.9 

53 

105 

112 

18 

63 

2.4 

34 

85 

40 

19 

61 

3.0 

40 

115 

140 

20 

57 

2.0 

53 

50 

30 

Average 

64.8 

2.8 

46.5 

119.5 

101.7 

63.5 

2.3 

45.7 

71.3 

44.2 

19251  FACTORS  INFLUENCING  LODGING  IN  CORN  363 

OJ.  /OJ.          ZOJ,          30JL          40-1,        50$          60-1.         70°f,         GO'fo         90J,         1001, 


Average  plant  height 
abort  ground 

Average  circumference 
at  base  of  stalks 


Average  number  of 
roots  per  plant 

Average  air-dry  weight 
of  aerial  ports 

Average  air-dry 
weight  of  roots 


FIG.  21. — CERTAIN  CHARACTERISTICS  OF  STRAIN  G-4-4-1  AS  COMPARED  ON  A  PERCENT- 
AGE BASIS  WITH  STRAIN  G-4-2-1 

Strain  G-4-2-1  in  each  case  represents  100  percent.   From  data  shown  in  Table  21. 

their  respective  parents.  This  shows  that  selection  still  had  an  effect  on 
this  strain  and  that  it  was  not  yet  homozygous. 

The  table  also  shows  clearly  that  the  average  dry  weight  of  roots, 
as  well  as  the  average  pulling  resistance  per  stalk,  correlates  indirectly 
with  the  average  percentage  of  leaning  stalks. 

A  few  first-generation  crosses  between  weak-rooted  and  strong- 
rooted  strains  have  been  grown.  When  a  cross  was  made  between 
pure-lines  A-1-1-2-R-3  and  B-1-1-1-R-8,  the  result  was  a  stand  of 
very  erect  plants.  In  several  other  cases,  little  lodging  occurred  when 
strong-rooted  and  weak-rooted  strains  were  crossed.  However,  when 
one  of  the  strong-rooted  A  strains  was  crossed  with  one  of  the  weak- 
rooted  HY  strains,  the  resulting  plants  lodged  practically  100  percent 

TABLE  22. — PULLING  RESISTANCE,  DRY  WEIGHT  OF  ROOTS,  AND  PERCENTAGES  OF  LEAN- 
ING PLANTS  IN  SEVERAL  SELF-FERTILIZED  STRAINS,  SHOWING  RELATION  OF 
INHERITED  STRONG  OR  WEAK  ROOT  ANCHORAGE  TO  PRO- 
PORTION OF  LEANING  PLANTS 


Factors  considered 

Strong  roots 

Weak  roots 

Strong  roots 

Weak  roots 

Average  pulling  resistance  of  50 
plants  in  parental  population 
(1922),  in  pounds  

(A-1-1-2-R-3) 
273.0 

(B-1-1-1-R-8) 
144.2 

(G-4-2) 
340.7 

(G-4-4) 
166.5 

Pulling  resistance  of  plant  chosen 
as  parent  (1922),  in  pounds  

460.0 

122.0 

720.0      * 

40.0 

Average  pulling  resistance  of  pro- 
geny of  above  plant  (1923),  in 
pounds  

(A-1-1-2-R-3-2) 

286  0    • 

(B-1-1-1-R-8-2) 

84.  5 

(G-4-2-1) 
400.7 

(G-4-4-1) 
161.2 

Average  air-dry  weight  of  roots 
per  plant  (1923),  in  grams  

79.6 

42.2 

101.7 

44.2 

Average  percentage  of  stalks 
leaning  30°  or  more  (1923)  

2.8 

90.5 

3.6 

28.2 

364 


BULLETIN  No.  266 


\_May, 


(Fig.  22).  This  indicates  that  the  inheritance  of  the  tendencies  to  strong 
and  weak  roots  is  not  to  be  explained  on  the  basis  of  a  single  genetic 
factor,  but  appears  to  be  more  complex  in  nature. 


FIG.   22. — FIRST-GENERATION    HYBRIDS    BETWEEN    WEAK-ROOTED    AND 
STRONG-ROOTED  SELF-FERTILIZED  STRAINS 

On  the  left,  a  plot  of  an  Fi  generation  cross  between  the  weak-rooted 
B  strain  and  the  strong-rooted  A  strain.  This  condition  resulted  in  a 
stand  of  very  erect  plants.  On  the  right,  a  plot  of  an  Fi  generation 
cross  between  the  weak-rooted  HY  strain  and  the  strong-rooted  A 
strain.  Altho  the  same  strong-rooted  parent  was  used  as  in  the  pre- 
vious case,  this  corn  lodged  100  percent.  Evidently  the  factors  for 
the  weak-rooted  and  strong-rooted  characters  are  not  a  single  pair  of 
allelomorphs. 


COMPARISON  OF  STALK  BREAKING  IN  SELF-FERTILIZED 
LINES  AND  FIRST-GENERATION  CROSSES 

Self-fertilized  strains  of  corn  vary  greatly  in  the  tendency  of  stalks 
to  break  during  the  latter  part  of  the  growing  season  and  after  maturity. 
Certain  strains  have  been  isolated  in  which  there  have  been  no  broken 
stalks  up  to  the  first  of  December  during  the  past  three  seasons.  In 
other  self-fertilized  strains,  under  the  same  conditions,  almost  all  the 
stalks  were  broken  within  two  or  three  weeks  after  maturity.  The 
inheritance  of  the  breaking  tendency  of  cornstalks  in  first-generation 
crosses  between  self-fertilized  lines,  and  its  effect  on  the  quality  of 
grain  are  given  in  Table  23. 


1925] 


FACTORS  INFLUENCING  LODGING  IN  CORN 


365 


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366 


BULLETIN  No.  266 


[May, 


Three  conditions,  which  are  heritable  to  a  large  extent,  are 
recognized  as  being  responsible  for  broken  stalks.  These  are  (1)  weak 
morphological  structure  of  the  stalks,  (2)  susceptibility  to  disease,  and 
(3)  susceptibility  to  frost  injury.  Under  morphological  structure  one 
must  consider  not  only  the  diameter  of  the  stalks  but  also  the  toughness 


FIG.  23. — BROKEX  STALKS  IN  FIRST-GENERATION  CROSSES 
All  three  of  these  rows  are  first-generation  crosses,  the  central 
row  being  HY901-1-5-5  X  W10-2-2  shown  in  Group  1,  Table 
23.  As  most  of  the  ears  came  in  contact  with  the  ground,  only 
a  small  percentage  of  them  were  marketable  at  harvest.  Both 
parents  had  a  strong  tendency  to  stalk  breaking. 


of  the  outer  shell,  or  cortex.  Frequently  a  stalk  will  stand  more  strain 
than  another  that  is  a  little  thicker,  due  to  the  toughness  of  the  hard 
outer  tissues. 

Infections  by  diseases  may  be  of  two  types;  systemic  and  local. 
Under  the  former,  infection  with  Aplanobacter  stezvarti  or  Cephalo- 
sporium  acremonium  would  no  doubt  be  important.  The  latter  organism 
was  found  to  cause  increases  in  broken  stalks  in  open-pollinated  strains 
(Table  10).  Local  infections  resulting  in  increases  in  the  percentages 
of  broken  stalks  may  be  caused  by  smut,  Diplodia,  Fusarium,  Gib- 


1925] 


FACTORS  INFLUENCING  LODGING  IN  CORN 


367 


berella,  and  probably  other  organisms.  Some  self-fertilized  strains  are 
especially  susceptible  to  one  or  several  of  the  diseases  caused  by  these 
organisms  and  the  stalks  often  break  over  early  at  the  infected  nodes. 
When  the  breaking  does  not  occur  until  after  maturity,  the  cause  is 
more  often  due  to  the  anatomical  structure  of  the  stalk. 


FIG.     24. — Two     CONTRASTING     Rows    OF     FIRST-GENERATION 
CROSSES 

On  the  right,  one  of  the  crosses  shown  in  Group  3,  and  on 
the  left,  one  of  the  crosses  shown  in  Group  5,  Table  23.  The 
high  percentage  of  broken  stalks  in  Group  5  was  due  largely  to 
frost  injury.  The  central  row  was  cut  out  before  photographing. 

In  the  case  of  low  resistance  to  frost  injury,  the  plants  die  when  a 
light,  early  frost  occurs,  while  the  more  hardy  strains  are  not  affected. 
After  death,  the  stalks  are  generally  invaded  by  saprophytic  organisms, 
and  by  the  time  a  month  has  passed  the  breaking  strength  of  the  stalks 
has  been  considerably  reduced. 

In  Group  1  (Table  23)  both  pistillate  and  pollinating  parents  con- 
tained a  very  high  percentage  of  broken  stalks.  The  first-generation 
crosses  between  these  two  strains  grew  vigorously  and  developed  large 
ears  on  almost  every  stalk.  However,  a  high  percentage  (71.0  percent 


368 


BULLETIN  No.  266 


[May, 


of  the  plants)  broke  very  early  in  the  fall  (Fig.  23),  and  as  a  result  the 
yield  of  grain  was  not  only  greatly  reduced  but  less  than  25  percent 
of  the  corn  was  sound.  In  Group  2,  where  only  one  of  the  parents  of 
the  cross  exhibited  a  tendency  to  stalk  breaking,  the  percentage  of 
broken  stalks  was  much  less,  being  reduced  from  71.0  to  22.9  percent. 


FIG.    25. — ONE   OF   THE    PARENTS   OF   THIS   FIRST-GENERATION 
CROSS  WAS  VERY  SUSCEPTIBLE  TO   FROST  INJURY 

The  central  row  shows  one  of  the  crosses  of  Group  4,  Table 
23.  An  early  frost  killed  this  row  while  the  adjoining  rows,  also 
first-generation  crosses,  were  but  slightly  affected.  Some  weeks 
later  the  stalks  broke  down,  as  here  illustrated. 

Furthermore,  the  relatively  low  percentage  of  breaking  in  Group  2 
occurred  much  later  in  the  season  and  as  a  result  there  was  little  injury 
to  the  quality  of  grain.  In  Group  3  both  parents  were  free  from  the 
stalk-breaking  tendency,  and  the  first-generation  cross  stood  up  well, 
even  to  the  last  of  November  (Fig.  24). 

During  the  fall  of  1924  much  variation  in  relative  resistance  to  frost 
injury  was  observed  among  the  self-fertilized  strains  growing  in  experi- 
mental plots  near  Bloomington.  In  the  cases  observed,  low  resistance  to 
frost  injury  apparently  was  dominant  to  high  resistance  to  frost  injury 


1925]  FACTORS  INFLUENCING  LODGING  IN  CORN  369 

(Table  23).  Plants  injured  by  early  frosts  were  much  more  easily 
broken  by  the  strong  winds  in  October  and  November.  In  Group  4, 
where  the  parents  contained  only  8.2  and  10.3  percent  of  broken  stalks, 
but  where  one  of  them  carried  low  resistance  to  frost  injury,  the  stalks 
in  the  cross  were  weakened  by  the  frost  injury  and  broke  under  the 
weight  of  the  heavy  ears  and  the  force  of  the  strong  prairie  winds 
(Fig.  25). 

Group  4  contained  about  as  many  broken  stalks  as  Group  1 — 70.3 
percent  as  compared  with  71.0  percent.  Plants  in  Group  5  (Fig.  24) 
were  not  affected  by  the  early  frost  which  killed  those  in  Group  4,  but 
were  killed  before  those  in  Group  3.  The  stalks  did  not  break  until 
they  were  fairly  dry;  consequently,  there  was  less  damaged  corn  than 
in  Group  4  (Table  23).  Altho  only  one  of  the  parents  in  Group  6 
exhibited  a  tendency  to  high  percentage  of  stalk  breaking,  the  plants 
were  killed  by  the  early  frosts  and  the  stalks  broke  soon  thereafter. 
As  a  result,  this  group  contained  65.1  percent  broken  stalks  as  com- 
pared with  22.9  percent  in  Group  2. 

It  is  evident  from  the  data  presented  in  Table  23  that  both  resis- 
tance to  frost  injury  and  resistance  to  stalk  breaking  can  be  controlled 
to  a  large  extent  by  careful  selections  within  self-fertilized  pure  lines 
and  by  proper  recombinations  of  these  pure  lines. 

SUMMARY 

In  the  study  of  lodging  in  corn  two  subdivisions  of  the  plants  were 
made:  namely,  those  having  "broken"  stalks  and  those  having  "leaning" 
stalks.  Stalks  inclining  30  degrees  or  more  were  considered  as  leaning 
stalks. 

In  studying  the  effect  of  corn  diseases  on  lodging,  experiments  were 
conducted  only  with  seed  infections  and  seed  inoculations.  While  all  of 
these  infections  and  inoculations  resulted  in  decreased  vigor  and  yield, 
not  all  of  them  increased  the  amount  of  lodging. 

Increases  in  the  percentage  of  leaning  stalks  occurred  when  seed 
was  infected  with  Diplodia  zeae,  when  starchy  seed  susceptible  to 
scutellum  rot  was  used,  or  when  the  seed  was  naturally  infected  or 
artificially  inoculated  with  Gibberella  saubinetii.  On  the  other  hand,  no 
significant  increases  in  the  percentage  of  leaning  plants  occurred  when 
seed  was  infected  with  Fusarium  moniliforme  or  Cephalosporium 
acremonium,  and  increases  were  doubtful  when  horny  seed  susceptible 
to  scutellum  rot  was  used. 

Increases  in  percentage  of  broken  stalks  due  to  seed  infection 
occurred  only  when  seed  was  infected  with  Cephalosporium  acremonium 
or  when  starchy  seed  susceptible  to  scutellum  rot  was  used. 

Commercial  strains  of  corn,  even  tho  practically  free  from  seed 
infection,  vary  considerably  in  respect  to  lodging. 


370  BULLETIN  No.  266  [May, 

The  time  of  planting,  whether  early  or  late  in  the  season,  may 
have  a  marked  influence  on  the  relative  percentage  of  both  leaning  and 
broken  stalks. 

Corn  planted  at  the  rate  of  two  kernels  to  a  hill  stood  more  erect 
than  that  planted  at  the  rate  of  three  kernels  to  a  hill. 

When  corn  followed  several  consecutive  corn  crops  on  the  same 
soil,  the  percentage  of  leaning  plants  was  much  greater  than  when  corn 
was  grown  to  succeed  virgin  sod  or  a  leguminous  crop.  The  percentage 
of  broken  stalks  was  not  affected  thereby. 

The  application  of  4  or  more  tons  of  limestone  per  acre  to  the  soil 
had  a  remarkable  effect  on  decreasing  the  percentage  of  leaning  plants. 
It  did  not,  however,  influence  the  percentage  of  broken  stalks,  nor  did 
it  have  a  marked  influence  on  the  yield  of  grain. 

Barren  stalks,  on  the  average,  leaned  to  a  greater  extent  than 
stalks  bearing  ears. 

In  a  number  of  self-fertilized  strains,  great  differences  in  respect 
to  lodging  were  observed,  even  tho  practically  disease-free  seed  was 
used  thruout.  Strains  that  grew  to  about  the  same  height,  of  which  one 
was  inclined  to  lodge  and  the  other  to  stand  erect,  were  studied,  and  the 
erect  strain  was  found  to  have  about  twice  as  great  a  root  system  as 
the  former.  Plants  having  a  tendency  to  lodge  also  were  found  to  have 
less  resistance  to  a  vertical  pull. 

Self-fertilized  strains  were  also  found  to  vary  greatly  in  the 
tendency  of  the  stalks  to  break  during  the  latter  part  of  the  growing 
season  and  after  maturity.  Some  strains  had  practically  no  broken 
stalks  up  to  the  time  winter  set  in,  while  many  others  were  broken  down 
completely  at  that  time.  These  differences  in  behavior  indicate  that  it 
may  not  be  difficult  to  develop  commercial  strains  that  will  have  very 
little  tendency  toward  stalk  breaking  even  under  adverse  conditions. 

It  is  evident  from  the  foregoing  that  some  of  the  corn  root  rot 
diseases  may  cause  increases  in  leaning  or  broken  stalks  of  corn,  but 
these  are  by  no  means  the  only  causes,  for  many  other  factors  such  as 
climate,  previous  cropping,  rate  and  time  of  planting,  and  soil  treatment, 
also  influence  the  amount  of  lodging. 


1925]  FACTORS  INFLUENCING  LODGING  OF  CORN  371 

LITERATURE  CITED 

1.  DlCKSON,   J.   G. 

1923.  Influence  of  soil  temperature  and  moisture  on  the  development  of  the 
seedling  blight  of  wheat  and  corn  caused  by  Gibberella  saubinetii. 
Jour.  Agr.  Res.  23,  837-870. 

2.  HOLBERT,   J.    R.,   DlCKSON,    J.    G.,    AND   BlGGAR,   H.    H. 

1920.  Correlation  of  early  growth,  variation  and  productivity  of  maize  as  in- 

fluenced by  certain  pathologic  factors.    Phytopath.    10,  57. 

3.  HOLBERT,  J.  R.,  BURLISON,  W.  L.,  BIGGAR,  H.  H.,  KOEIILER,  BENJAMIN,  DUNCAN, 

G.  H.,  AND  JENKINS,  M.  T. 

1923.  Early  vigor  of  maize  plants  and  yield  of  grain  as  influenced  by  the  corn 

root,  stalk  and  ear  rot  diseases.   Jour.  Agr.  Res.    23,  583-629. 

4.  HOLBERT,  J.  R.,  BURLISON,  W.  L.,  KOEHLER,  BENJAMIN,  WOODWORTH,  C.  M.,  AND 

DUNCAN,  GEORGE  H. 

1924.  The  corn  root,  stalk,  and  ear  rot  diseases  and  their  control  by  seed  se- 

lection and  breeding.   Ill  Agr.  Exp.  Sta.  Bui.  255. 

5.  HOLBERT,  J.  R.,  KOEHLER,  BENJAMIN 

1924.    Anchorage  and  extent  of  corn  root  systems.   Jour.  Agr.  Res.    27,  71-78. 

6.  KOEHLER,  B.,  DICKSON,  J.  G.,  AND  HOLBERT,  J.  R. 

1924.  Wheat  scab  and  corn  root-rot  caused  by  Giberella  saubinetii  in  relation 
to  crop  successions.  Jour.  Agr.  Res.  27,  861-879. 

7.  REDDY,  C.  S.,  AND  HOLBERT,  J.  R. 

1924.     The  black-bundle  disease  of  corn.   Jour.  Agr.  Res.  27,  177-205. 

8.  ROSEN,  H.  R. 

1921.  Further  observations  on   a   bacterial   root-   and   stalk-rot   of   field   corn. 

Phytopath.    11,  74-79. 

9.  STUDENT  TABLES  FOR  ESTIMATING  PROBABILITY 

1917.     Biometrika.    11,  414-417. 
10.  TROST,  J.  F. 

1922.  Relation  of  the  character  of  the  endosperm  to  the  susceptibility  of  dent 

corn  to  root  rotting.     U.  S.  Dept.  Agr.  Bui.  1062,  7. 


WT     TV      TV        X1 


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